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Structural, magnetic and magnetocaloric performances in Cu18Al25Ho57 and Cu18Al25Tm57 amorphous ribbons
Journal of Magnetism and Magnetic Materials 495 (2020) 165888
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Research articles
Structural, magnetic and magnetocaloric performances in Cu18Al25Ho57 and Cu18Al25Tm57 amorphous ribbons Zhongqi Dong, Suhua Yin
T
⁎
Department of Material Engineering, Hebei College of Industry and Technology, Shijiazhuang 050091, PR China
A R T I C LE I N FO
A B S T R A C T
Keywords: Magnetocaloric effect Amorphous ribbons Magnetic properties Magnetic refrigeration
The rapidly solidified Cu18Al25Ho57 and Cu18Al25Tm57 melt-spun ribbons have been successfully synthesized. Both ribbons show complete amorphous characteristics based on the analysis of the X-ray diffraction (XRD) and differential scanning calorimeter (DSC). Magnetic measurements illustrate that a paramagnetic to ferromagnetic type transition takes place at Curie temperatures TC of 22.2 and 4.9 K for Cu18Al25Ho57 and Cu18Al25Tm57, respectively, which are companied with a considerable magnetocaloric effect (MCE). For a magnetic field change (ΔH ) of 0–7 T, Cu18Al25Ho57 and Cu18Al25Tm57 ribbons display the maximum magnetic entropy (ΔSMmax ) of 24.8 and 20.9 J kg−1 K−1, the refrigerant capacity (RC) determined from the area below a full-width at half-maximum (δTFWHM ) forΔS (T ) curve of 582.9 and 385 J kg−1, respectively. The large MCEs at low temperatures demonstrate that Cu18Al25RE57 (RE = Ho and Tm) are competitive candidates among the MCE materials working at liquid hydrogen and liquid helium temperature zones.
Nowadays, the magnetic refrigeration (MR) based on magnetocaloric effect (MCE) has taken as a promising alternative technology because of their potential advantages over the present well commercialized gas compression/expansion technology, high energy-efficiency and low environment impact [1–6]. The MCE is noted as one of the most interesting performances and has been intensively investigated for the magnetic material with aim of suppressing the emission of pollution components. However, the MR is still uncompetitive with gas compression/expansion technology owing to lack of high-performing materials exhibiting large MCEs in magnetic fields low enough. As a results, a number of magnetic solids with large/giant MCE have been realized, including MnAs [7,8], (La,M)MnO3 [9,10], Ni-Mn-X [11–15], La(Fe,Si)13 [16,17], MnTX [18,19] and some rare earth (RE) based materials [20–25]. In the past few decades, many investigations have revealed that some amorphous alloys are the most fascinating MCE materials, due to its high chemical stability, good thermal conductivity, and low electrical conductivity [26–28]. Generally, the peak values of −ΔSM in the amorphous materials are lower than those of crystallize ones. Therefore, some previous reports were dedicated to improve the peak values of −ΔSM for amorphous MCE materials. The investigation of cryogenic (around and below 20 K) MCE materials, most researchers are focusing on rare earth (RE) based alloys or oxides [29–34]. In fact, some RE-rich alloys and oxides are exhibiting rather sharp and high peak values in
⁎
−ΔSM curves near their respective transition temperatures. In the view of the practical application, one expects that the MCE materials should possess a large value in −ΔSM and at a wide temperature region. As for the amorphous materials, the magnetic transition could be broadened which further may widen the peak in −ΔSM curves. Therefore, to synthesize and design more amorphous materials with outstanding MCE performance remain an important goal for solid-state science. Here, we report the MCE in rapidly solidified Cu18Al25Ho57 and Cu18Al25Tm57 ribbons. A rather large tunable reversible MCE was obtained in Cu18Al25RE57 amorphous alloys with a wide temperature range. 1. Experimental Cu18Al25Ho57 and Cu18Al25Tm57 ingots were prepared in approximately 4 g quantities by arc-melting the stoichiometric amounts of starting metals on a water cooled copper hearth under argon gas atmosphere. Cu and Al were at least 99.99% pure, while rare earths (Ho and Tm) were 99.9% pure with respect to other metals. The alloy ingots were turned over and re-melted for four times, and the total weight losses were not more than 0.5 wt%. The melt-spun ribbons were prepared using induction melting the as-solidified alloy ingots at 1273 K to 1373 K in a quartz crucible onto a chilled Cu wheel spinning under Ar gas. The obtained ribbons generally were with a typical feature
Corresponding author. E-mail address: [email protected] (S. Yin).
https://doi.org/10.1016/j.jmmm.2019.165888 Received 22 July 2019; Received in revised form 14 September 2019; Accepted 22 September 2019 Available online 23 September 2019 0304-8853/ © 2019 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials 495 (2020) 165888
Z. Dong and S. Yin
Fig. 3. The magnetization (M, left scale0 and reciprocal susceptibility (1/χ, right scale) as a function of temperature for melt-spun Cu18Al25Ho57 under a magnetic field of 1 T. The insets show the temperature dependence of magnetization (M) under a magnetic field (H) of 0.2 T (left scale) in the field-cooling (FC) and zero-field-cooling (ZFC) modes and dMFC/dT (right scale) for meltspun Cu18Al25Ho57 ribbons.
Fig. 1. The XRD patterns for melt-spun Cu18Al25Ho57 and Cu18Al25Tm57 ribbons at room temperature.
of ~ 2.1 mm in width and 22–33 μm in thickness. Identification of microstructure was carried out using “D/max-2550, Rigaku” X-ray diffraction (XRD) at room temperature. The amorphous characteristics was analyzed using “Rigaku Thermo plus EVO2 TG-DTA 8121” Thermogravimetric (TG-DSC) analyzer. Magnetic characterization as a function of both temperature and magnetic field was performed for present Cu18Al25Ho57 and Cu18Al25Tm57 ribbons using a commercial Physical Property Measurement System (Quantum Design, USA) with a vibrating sample magnetometer (VSM) inset.
values Tx (first crystallization temperature), Tg (glassy transition temperature), Tm (melting point) and Tl (liquidus temperature) are obtained to be 600.9, 626.8, 1083.9 and 1162.3 K for Cu18Al25Ho57, as well as to be 622.3, 638.4, 1187.3 and 1211.1 K for Cu18Al25Tm57, respectively. Furthermore, one of the key glass forming ability (GFA) factors, undercooled liquid region value [ΔTx (=Tx − Tg)], are computed to be 25.9 and 16.1 K for Cu18Al25Ho57 and Cu18Al25Tm57 ribbons, respectively. Magnetization M as a function of temperature (T) in zero-fieldcooling (ZFC) and field-cooling (FC) modes recorded in the temperature range of 3–58 K under an applied magnetic field (H) of 0.2 T for Cu18Al25Ho57 and Cu18Al25Tm57 samples are given in the insets of Figs. 3 and 4. It can note that the M(T) curves for both ribbons display a similar behaviour, and they can overlap with each other in ZFC and FC modes. The M(T) curves clearly indicate that Cu18Al25RE57 (RE = Ho and Tm) pass through a FM (ferromagnetic) to PM (paramagnetic) type transition, where the Curie temperatures (TC) are determined to be 22.2, and 4.9 K from the inflexion point of dM/dT vs. T curves (see insets of Figs. 3 and 4) for Cu18Al25Ho57 and Cu18Al25Tm57, respectively. The temperature dependence of magnetization M for Cu18Al25Ho57 and Cu18Al25Tm57 alloys measured under an applied H of
2. Results and discussion The experimental powder XRD study at room temperature for Cu18Al25Ho57 and Cu18Al25Tm57 ribbons are presented in Fig. 1. A significantly broad diffraction peak at the maximum 2θ approximately 35° without any sharp crystalline peaks for both ribbons can be observed. Thus, it is reasonable assume that the complete amorphous state is formed in both samples. To study the characterization of amorphous further, we performed the DSC analysis at a heating rate of 20 K/min, and the corresponding DSC traces for Cu18Al25Ho57 and Cu18Al25Tm57 ribbons are given in Fig. 2. A typical amorphous transition characterized by a weak endothermic reaction peak is demonstrated in both samples, and the enlarge curves at the temperature between 570 K and 690 K are given in the inset of Fig. 2. From the Fig. 2, several featured
Fig. 4. The magnetization (M, left scale) and reciprocal susceptibility (1/χ, right scale) as a function of temperature for melt-spun Cu18Al25Tm57 under a magnetic field of 1 T. The insets show the temperature dependence of magnetization (M) under a magnetic field (H) of 0.2 T (left scale) in the field-cooling (FC) and zero-field-cooling (ZFC) modes and dMFC/dT (right scale) for meltspun Cu18Al25Tm57 ribbons.
Fig. 2. The DSC traces for melt-spun Cu18Al25Ho57 and Cu18Al25Tm57 ribbons. 2
Journal of Magnetism and Magnetic Materials 495 (2020) 165888
Z. Dong and S. Yin
Fig. 5. The magnetic field dependence of magnetization (a) and the plots of H/ M versus M2 (b) for melt-spun Cu18Al25Ho57 amorphous ribbons.
Fig. 6. The magnetic field dependence of magnetization (a) and the plots of H/ M versus M2 (b) for melt-spun Cu18Al25Tm57 amorphous ribbons.
1T are displayed in Figs. 3 and 4. Then, the corresponding inverse magnetic susceptibility 1/χ deduced from M (T) are also given on the right hand of Figs. 3 and 4. A similarly linear transition relation can be observed for both samples above TC, and the 1/ χ curves follow the Curie-Weiss law. From the linear fit of the paramagnetic part, the effective magnetic moments (μeff) of the Ho and Tm atoms are calculated to be 10.62 and 7.64 μB, respectively, where the values are rather close to the expected theoretical ones. Furthermore, the paramagnetic Curie temperatures (θ p) are 15.4 and 2.4 K for Cu18Al25Ho57 and Cu18Al25Tm57 ribbons, respectively. The obtained positive values in θ p further confirm the FM interaction in the ground state. The magnetic isotherms M (H) through their magnetic phase transition temperatures for Cu18Al25Ho57 and Cu18Al25Tm57 were determined to evaluated the MCE performances. Several M (H) isotherms registered in magnetic field change up to 0–7 T in the temperature ranges from 3 to 50 K and 3–38 K for Cu18Al25Ho57 and Cu18Al25Tm57 are illustrated in Fig. 5 (a) and 6 (a), respectively. These M (H) curves in both ribbons present similar characteristics, where M continuously increases at low temperatures in weak magnetic fields and then rises gradually with increasing magnetic field. However, there is no signal of saturation can be found even at 0–7 T for both ribbons. We draw in Figs. 5(b) and 6(b) the Arrott plots (M2 vs. H/M) isotherms to further define the order of the magnetic phase transition. Generally, the order could be checked based on the slope from the figure from the Banerjee’s criterion [35]. A positive or negative sign of the slope relates to a second- or first-order magnetic phase transition. For present samples, it can be seen clearly that all curves show positive slope in the whole field regions, confirming the FM to PM type transition is of a second order. The M (H) curves were utilized to evaluate the magnetic entropy change (-ΔSM), which is associated with the MCE under the effect of a magnetic field. Based on thermo-dynamical theory, the magnetic part of entropy change (ΔSM), induced by modifying the magnetic field change (ΔH) from 0 to a certain value, can be approximately as [1–3,6]:
ΔSM (T , ΔH ) = SM (T , H ) − SM (T , 0) =
∫0
Hmax
⎛ ∂S (H , T ) ⎞ dH ⎝ ∂H ⎠T
(1)
Following Maxwell’s relation:
⎛ ∂S (H , T ) ⎞ = ⎛ ∂M (H , T ) ⎞ ∂T ⎝ ∂H ⎠T ⎝ ⎠H
(2)
then, the relationship can be described:
ΔSM (T , ΔH ) =
∫0
Hmax
⎛ ∂M (H , T ) ⎞ dH ∂T ⎝ ⎠H
(3)
In the case of the M (H, T) data measured at a small discrete temperature and field intervals, ΔSM can be approximated by:
ΔSM (T , ΔH ) =
∑ i
Mi + 1 (Ti + 1, H ) − Mi (Ti , H ) ΔH Ti + 1 − Ti
(4)
The calculated −ΔSM(T) curves for both samples calculated by using Eq. (4) under different applied magnetic fields are represented in Fig. 7. Notably, the −ΔSM(T) curves with temperature display a very similar behaviour for both ribbons, i. e., a pronounced peak is close to its own TC, and then it decreases continuously and gradually when the temperatures away from TC. The maximum values of −ΔSM (−ΔSMmax) are 6.8, 18.5 and 24.8 J kg−1 K−1 for Cu18Al25Ho57, as well as 10.7, 18.2 and 20.9 J kg−1 K−1 for Cu18Al25Tm57 under the ΔH of 0–2, 0–5 and 0–7 T, respectively. To further probe the order of magnetic phase transition, the phenomenological universal curve [36,37] has also been applied to provide evidence. Generally, the criterion is built up by normalizing each magnetic entropy change curve against their respective maximum max − ΔSMmax , i.e., ΔS′ (ΔS′ = ΔSM (T )/ΔSM ), which is taken as new Y-axis, and the rescaling temperature, θ, is taken as updated X-axis, it can be described as: 3
Journal of Magnetism and Magnetic Materials 495 (2020) 165888
Z. Dong and S. Yin
Table 1 The MCE parameters (TC, −ΔSMmax, RC and RCP) with the ΔH of 0–5 T for amorphousized Cu18Al25Ho57 and Cu18Al25Tm57 ribbons as well as some outstanding MCE materials with similar TC.
T ≤ TC T > TC
(5)
where Tr1 and Tr2 present two reference temperatures below and above TC, which satisfy the relation,
ΔSM (Tr1) = ΔSM (Tr 2) = f × ΔSMmax
TC (K)
−ΔSMmax (J kg−1 K−1)
RC (J kg−1)
RCP (J kg−1)
Refs.
Cu18Al25Ho57 Cu18Al25Tm57 TmAgAl Ho30Y26Al24Co20 Tm60Co20Ni20 Er2Ni2Ga TmZn Tm2Cu2Cd Ho36Dy20Al24Co20 HoPdIn Ho57Cu25Al18 Er2Co2Ga
22.2 4.9 3.3 5.5 6.7 7.1 8.4 15 17 23 24.4 25.5
18.5 18.2 12.4 10.8 17.1 9.62 26.9 17.3 11.8 14.6 11.8 9.6
368.0 258.5 214 241 ~205 151 214 165 365 ~374 385 162
485.0 334.5 166 313 273 ~201 269 218 344 496 482 223
present present [38] [25] [39] [40] [41] [42] [43] [44] [45] [46]
cooling power (RCP) have been widely applied to check the cooling efficiency of the MCE materials. Both parameters correspond to the amount of the heat could transfer from cold to hot tanks. The detailed description can be found somewhere in several review papers [1–3,6]. The values of RC (RCP) under the ΔH of 0–2, 0–5 and 0–7 T are 110.2 (151.8), 368.0 (485.0) and 582.6 (741.8) J kg−1 for Cu18Al25Ho57, and 93.0 (121.2), 258.5 (334.5) and 385.3 (509.5) J kg−1 for Cu18Al25Tm57, respectively. Moreover, several typical MCE factors (TC, −ΔSMmax, RCP and RC) with ΔH of 0–5 T for present amorphous Cu18Al25RE57 ribbons are summarized in Table 1, together with some other MCE materials for comparison. The MCE factors, especially for the values of RC, are quite considerable and comparable with some reported promising MCE candidates in the literature. On the other hand, if an ideal MR Ericsson cycle [47,48] is taken account, it is better that the MCE materials have a constant −ΔSM over a rather wide working temperature range. Therefore, a composite MCE material method has been preferred by selecting or designing materials with near working temperature and similar magnitude in MCE performance [32,34,42,49]. We can see that the present Cu18Al25Ho57 and Cu18Al25Tm57 amorphous ribbons can achieve the above criterion by adjusting the rare earth ratios only, which covers a 6–42 K wide temperature range. Considering the large −ΔSM with no thermal/magnetic hysteresis accompanied with considerable RC and RCP values indicate that the Cu18Al25Ho57 and Cu18Al25Tm57 amorphous ribbons are potential coolants for cryogenic application.
Fig. 7. The magnetic entropy change −ΔSM as a function of temperature for melt-spun Cu18Al25Ho57 (a) and Cu18Al25Tm57 (b) with the magnetic field changes from 0 to 1 to 0–7 T.
− (T − TC )/(Tr 1 − TC ); θ=⎧ ⎨ ⎩ (T − TC )/(Tr 2 − TC );
Materials
(6)
with f = 0.6 for the present study. Fig. 8 shows ΔS′ as a function of θ for both samples. It can be obviously note that the experimental data for different H distribute on one master curve, which verifies the magnetic phase transition of Cu18Al25Ho57 and Cu18Al25Tm57 ribbons is a second order. The factors of refrigerant capacity (RC) as well as the relative
3. Conclusions In short, two amorphousized Cu18Al25RE57 ribbons with RE of Ho and Tm were prepared successfully by a conventional melt-spinning technology, and a detailed of the GFA, magnetic and cryogenic MCE properties were studied. Both ribbons mentioned here undergo a typical PM to FM (second ordered) type transition, resulting in large MCEs in a wide temperature range. The MCE factors of −ΔSMmax, RC and RCP are 18.5 J kg−1 K−1, 368.0 and 484.9 J kg−1 for Cu18Al25RE57, as well as 18.2 J kg−1 K−1, 258.5 and 334.5 J kg−1 for Cu18Al25Tm57 under ΔH of 0–5 T, respectively. The similarly fascinating MCE performances together with near working temperatures make Cu18Al25RE57 amorphous ribbons competitive among active cryogenic MCE materials.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Fig. 8. Normalized magnetic entropy change (ΔS′ = ΔSM(T)/ΔSMmax) as a function of rescaled temperature (θ) at different ΔH for melt-spun Cu18Al25Ho57 (a) and Cu18Al25Tm57 (b) ribbons. 4
Journal of Magnetism and Magnetic Materials 495 (2020) 165888
Z. Dong and S. Yin
Acknowledgement
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5
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Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Research articles
Structural, magnetic and magnetocaloric performances in Cu18Al25Ho57 and Cu18Al25Tm57 amorphous ribbons Zhongqi Dong, Suhua Yin
T
⁎
Department of Material Engineering, Hebei College of Industry and Technology, Shijiazhuang 050091, PR China
A R T I C LE I N FO
A B S T R A C T
Keywords: Magnetocaloric effect Amorphous ribbons Magnetic properties Magnetic refrigeration
The rapidly solidified Cu18Al25Ho57 and Cu18Al25Tm57 melt-spun ribbons have been successfully synthesized. Both ribbons show complete amorphous characteristics based on the analysis of the X-ray diffraction (XRD) and differential scanning calorimeter (DSC). Magnetic measurements illustrate that a paramagnetic to ferromagnetic type transition takes place at Curie temperatures TC of 22.2 and 4.9 K for Cu18Al25Ho57 and Cu18Al25Tm57, respectively, which are companied with a considerable magnetocaloric effect (MCE). For a magnetic field change (ΔH ) of 0–7 T, Cu18Al25Ho57 and Cu18Al25Tm57 ribbons display the maximum magnetic entropy (ΔSMmax ) of 24.8 and 20.9 J kg−1 K−1, the refrigerant capacity (RC) determined from the area below a full-width at half-maximum (δTFWHM ) forΔS (T ) curve of 582.9 and 385 J kg−1, respectively. The large MCEs at low temperatures demonstrate that Cu18Al25RE57 (RE = Ho and Tm) are competitive candidates among the MCE materials working at liquid hydrogen and liquid helium temperature zones.
Nowadays, the magnetic refrigeration (MR) based on magnetocaloric effect (MCE) has taken as a promising alternative technology because of their potential advantages over the present well commercialized gas compression/expansion technology, high energy-efficiency and low environment impact [1–6]. The MCE is noted as one of the most interesting performances and has been intensively investigated for the magnetic material with aim of suppressing the emission of pollution components. However, the MR is still uncompetitive with gas compression/expansion technology owing to lack of high-performing materials exhibiting large MCEs in magnetic fields low enough. As a results, a number of magnetic solids with large/giant MCE have been realized, including MnAs [7,8], (La,M)MnO3 [9,10], Ni-Mn-X [11–15], La(Fe,Si)13 [16,17], MnTX [18,19] and some rare earth (RE) based materials [20–25]. In the past few decades, many investigations have revealed that some amorphous alloys are the most fascinating MCE materials, due to its high chemical stability, good thermal conductivity, and low electrical conductivity [26–28]. Generally, the peak values of −ΔSM in the amorphous materials are lower than those of crystallize ones. Therefore, some previous reports were dedicated to improve the peak values of −ΔSM for amorphous MCE materials. The investigation of cryogenic (around and below 20 K) MCE materials, most researchers are focusing on rare earth (RE) based alloys or oxides [29–34]. In fact, some RE-rich alloys and oxides are exhibiting rather sharp and high peak values in
⁎
−ΔSM curves near their respective transition temperatures. In the view of the practical application, one expects that the MCE materials should possess a large value in −ΔSM and at a wide temperature region. As for the amorphous materials, the magnetic transition could be broadened which further may widen the peak in −ΔSM curves. Therefore, to synthesize and design more amorphous materials with outstanding MCE performance remain an important goal for solid-state science. Here, we report the MCE in rapidly solidified Cu18Al25Ho57 and Cu18Al25Tm57 ribbons. A rather large tunable reversible MCE was obtained in Cu18Al25RE57 amorphous alloys with a wide temperature range. 1. Experimental Cu18Al25Ho57 and Cu18Al25Tm57 ingots were prepared in approximately 4 g quantities by arc-melting the stoichiometric amounts of starting metals on a water cooled copper hearth under argon gas atmosphere. Cu and Al were at least 99.99% pure, while rare earths (Ho and Tm) were 99.9% pure with respect to other metals. The alloy ingots were turned over and re-melted for four times, and the total weight losses were not more than 0.5 wt%. The melt-spun ribbons were prepared using induction melting the as-solidified alloy ingots at 1273 K to 1373 K in a quartz crucible onto a chilled Cu wheel spinning under Ar gas. The obtained ribbons generally were with a typical feature
Corresponding author. E-mail address: [email protected] (S. Yin).
https://doi.org/10.1016/j.jmmm.2019.165888 Received 22 July 2019; Received in revised form 14 September 2019; Accepted 22 September 2019 Available online 23 September 2019 0304-8853/ © 2019 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials 495 (2020) 165888
Z. Dong and S. Yin
Fig. 3. The magnetization (M, left scale0 and reciprocal susceptibility (1/χ, right scale) as a function of temperature for melt-spun Cu18Al25Ho57 under a magnetic field of 1 T. The insets show the temperature dependence of magnetization (M) under a magnetic field (H) of 0.2 T (left scale) in the field-cooling (FC) and zero-field-cooling (ZFC) modes and dMFC/dT (right scale) for meltspun Cu18Al25Ho57 ribbons.
Fig. 1. The XRD patterns for melt-spun Cu18Al25Ho57 and Cu18Al25Tm57 ribbons at room temperature.
of ~ 2.1 mm in width and 22–33 μm in thickness. Identification of microstructure was carried out using “D/max-2550, Rigaku” X-ray diffraction (XRD) at room temperature. The amorphous characteristics was analyzed using “Rigaku Thermo plus EVO2 TG-DTA 8121” Thermogravimetric (TG-DSC) analyzer. Magnetic characterization as a function of both temperature and magnetic field was performed for present Cu18Al25Ho57 and Cu18Al25Tm57 ribbons using a commercial Physical Property Measurement System (Quantum Design, USA) with a vibrating sample magnetometer (VSM) inset.
values Tx (first crystallization temperature), Tg (glassy transition temperature), Tm (melting point) and Tl (liquidus temperature) are obtained to be 600.9, 626.8, 1083.9 and 1162.3 K for Cu18Al25Ho57, as well as to be 622.3, 638.4, 1187.3 and 1211.1 K for Cu18Al25Tm57, respectively. Furthermore, one of the key glass forming ability (GFA) factors, undercooled liquid region value [ΔTx (=Tx − Tg)], are computed to be 25.9 and 16.1 K for Cu18Al25Ho57 and Cu18Al25Tm57 ribbons, respectively. Magnetization M as a function of temperature (T) in zero-fieldcooling (ZFC) and field-cooling (FC) modes recorded in the temperature range of 3–58 K under an applied magnetic field (H) of 0.2 T for Cu18Al25Ho57 and Cu18Al25Tm57 samples are given in the insets of Figs. 3 and 4. It can note that the M(T) curves for both ribbons display a similar behaviour, and they can overlap with each other in ZFC and FC modes. The M(T) curves clearly indicate that Cu18Al25RE57 (RE = Ho and Tm) pass through a FM (ferromagnetic) to PM (paramagnetic) type transition, where the Curie temperatures (TC) are determined to be 22.2, and 4.9 K from the inflexion point of dM/dT vs. T curves (see insets of Figs. 3 and 4) for Cu18Al25Ho57 and Cu18Al25Tm57, respectively. The temperature dependence of magnetization M for Cu18Al25Ho57 and Cu18Al25Tm57 alloys measured under an applied H of
2. Results and discussion The experimental powder XRD study at room temperature for Cu18Al25Ho57 and Cu18Al25Tm57 ribbons are presented in Fig. 1. A significantly broad diffraction peak at the maximum 2θ approximately 35° without any sharp crystalline peaks for both ribbons can be observed. Thus, it is reasonable assume that the complete amorphous state is formed in both samples. To study the characterization of amorphous further, we performed the DSC analysis at a heating rate of 20 K/min, and the corresponding DSC traces for Cu18Al25Ho57 and Cu18Al25Tm57 ribbons are given in Fig. 2. A typical amorphous transition characterized by a weak endothermic reaction peak is demonstrated in both samples, and the enlarge curves at the temperature between 570 K and 690 K are given in the inset of Fig. 2. From the Fig. 2, several featured
Fig. 4. The magnetization (M, left scale) and reciprocal susceptibility (1/χ, right scale) as a function of temperature for melt-spun Cu18Al25Tm57 under a magnetic field of 1 T. The insets show the temperature dependence of magnetization (M) under a magnetic field (H) of 0.2 T (left scale) in the field-cooling (FC) and zero-field-cooling (ZFC) modes and dMFC/dT (right scale) for meltspun Cu18Al25Tm57 ribbons.
Fig. 2. The DSC traces for melt-spun Cu18Al25Ho57 and Cu18Al25Tm57 ribbons. 2
Journal of Magnetism and Magnetic Materials 495 (2020) 165888
Z. Dong and S. Yin
Fig. 5. The magnetic field dependence of magnetization (a) and the plots of H/ M versus M2 (b) for melt-spun Cu18Al25Ho57 amorphous ribbons.
Fig. 6. The magnetic field dependence of magnetization (a) and the plots of H/ M versus M2 (b) for melt-spun Cu18Al25Tm57 amorphous ribbons.
1T are displayed in Figs. 3 and 4. Then, the corresponding inverse magnetic susceptibility 1/χ deduced from M (T) are also given on the right hand of Figs. 3 and 4. A similarly linear transition relation can be observed for both samples above TC, and the 1/ χ curves follow the Curie-Weiss law. From the linear fit of the paramagnetic part, the effective magnetic moments (μeff) of the Ho and Tm atoms are calculated to be 10.62 and 7.64 μB, respectively, where the values are rather close to the expected theoretical ones. Furthermore, the paramagnetic Curie temperatures (θ p) are 15.4 and 2.4 K for Cu18Al25Ho57 and Cu18Al25Tm57 ribbons, respectively. The obtained positive values in θ p further confirm the FM interaction in the ground state. The magnetic isotherms M (H) through their magnetic phase transition temperatures for Cu18Al25Ho57 and Cu18Al25Tm57 were determined to evaluated the MCE performances. Several M (H) isotherms registered in magnetic field change up to 0–7 T in the temperature ranges from 3 to 50 K and 3–38 K for Cu18Al25Ho57 and Cu18Al25Tm57 are illustrated in Fig. 5 (a) and 6 (a), respectively. These M (H) curves in both ribbons present similar characteristics, where M continuously increases at low temperatures in weak magnetic fields and then rises gradually with increasing magnetic field. However, there is no signal of saturation can be found even at 0–7 T for both ribbons. We draw in Figs. 5(b) and 6(b) the Arrott plots (M2 vs. H/M) isotherms to further define the order of the magnetic phase transition. Generally, the order could be checked based on the slope from the figure from the Banerjee’s criterion [35]. A positive or negative sign of the slope relates to a second- or first-order magnetic phase transition. For present samples, it can be seen clearly that all curves show positive slope in the whole field regions, confirming the FM to PM type transition is of a second order. The M (H) curves were utilized to evaluate the magnetic entropy change (-ΔSM), which is associated with the MCE under the effect of a magnetic field. Based on thermo-dynamical theory, the magnetic part of entropy change (ΔSM), induced by modifying the magnetic field change (ΔH) from 0 to a certain value, can be approximately as [1–3,6]:
ΔSM (T , ΔH ) = SM (T , H ) − SM (T , 0) =
∫0
Hmax
⎛ ∂S (H , T ) ⎞ dH ⎝ ∂H ⎠T
(1)
Following Maxwell’s relation:
⎛ ∂S (H , T ) ⎞ = ⎛ ∂M (H , T ) ⎞ ∂T ⎝ ∂H ⎠T ⎝ ⎠H
(2)
then, the relationship can be described:
ΔSM (T , ΔH ) =
∫0
Hmax
⎛ ∂M (H , T ) ⎞ dH ∂T ⎝ ⎠H
(3)
In the case of the M (H, T) data measured at a small discrete temperature and field intervals, ΔSM can be approximated by:
ΔSM (T , ΔH ) =
∑ i
Mi + 1 (Ti + 1, H ) − Mi (Ti , H ) ΔH Ti + 1 − Ti
(4)
The calculated −ΔSM(T) curves for both samples calculated by using Eq. (4) under different applied magnetic fields are represented in Fig. 7. Notably, the −ΔSM(T) curves with temperature display a very similar behaviour for both ribbons, i. e., a pronounced peak is close to its own TC, and then it decreases continuously and gradually when the temperatures away from TC. The maximum values of −ΔSM (−ΔSMmax) are 6.8, 18.5 and 24.8 J kg−1 K−1 for Cu18Al25Ho57, as well as 10.7, 18.2 and 20.9 J kg−1 K−1 for Cu18Al25Tm57 under the ΔH of 0–2, 0–5 and 0–7 T, respectively. To further probe the order of magnetic phase transition, the phenomenological universal curve [36,37] has also been applied to provide evidence. Generally, the criterion is built up by normalizing each magnetic entropy change curve against their respective maximum max − ΔSMmax , i.e., ΔS′ (ΔS′ = ΔSM (T )/ΔSM ), which is taken as new Y-axis, and the rescaling temperature, θ, is taken as updated X-axis, it can be described as: 3
Journal of Magnetism and Magnetic Materials 495 (2020) 165888
Z. Dong and S. Yin
Table 1 The MCE parameters (TC, −ΔSMmax, RC and RCP) with the ΔH of 0–5 T for amorphousized Cu18Al25Ho57 and Cu18Al25Tm57 ribbons as well as some outstanding MCE materials with similar TC.
T ≤ TC T > TC
(5)
where Tr1 and Tr2 present two reference temperatures below and above TC, which satisfy the relation,
ΔSM (Tr1) = ΔSM (Tr 2) = f × ΔSMmax
TC (K)
−ΔSMmax (J kg−1 K−1)
RC (J kg−1)
RCP (J kg−1)
Refs.
Cu18Al25Ho57 Cu18Al25Tm57 TmAgAl Ho30Y26Al24Co20 Tm60Co20Ni20 Er2Ni2Ga TmZn Tm2Cu2Cd Ho36Dy20Al24Co20 HoPdIn Ho57Cu25Al18 Er2Co2Ga
22.2 4.9 3.3 5.5 6.7 7.1 8.4 15 17 23 24.4 25.5
18.5 18.2 12.4 10.8 17.1 9.62 26.9 17.3 11.8 14.6 11.8 9.6
368.0 258.5 214 241 ~205 151 214 165 365 ~374 385 162
485.0 334.5 166 313 273 ~201 269 218 344 496 482 223
present present [38] [25] [39] [40] [41] [42] [43] [44] [45] [46]
cooling power (RCP) have been widely applied to check the cooling efficiency of the MCE materials. Both parameters correspond to the amount of the heat could transfer from cold to hot tanks. The detailed description can be found somewhere in several review papers [1–3,6]. The values of RC (RCP) under the ΔH of 0–2, 0–5 and 0–7 T are 110.2 (151.8), 368.0 (485.0) and 582.6 (741.8) J kg−1 for Cu18Al25Ho57, and 93.0 (121.2), 258.5 (334.5) and 385.3 (509.5) J kg−1 for Cu18Al25Tm57, respectively. Moreover, several typical MCE factors (TC, −ΔSMmax, RCP and RC) with ΔH of 0–5 T for present amorphous Cu18Al25RE57 ribbons are summarized in Table 1, together with some other MCE materials for comparison. The MCE factors, especially for the values of RC, are quite considerable and comparable with some reported promising MCE candidates in the literature. On the other hand, if an ideal MR Ericsson cycle [47,48] is taken account, it is better that the MCE materials have a constant −ΔSM over a rather wide working temperature range. Therefore, a composite MCE material method has been preferred by selecting or designing materials with near working temperature and similar magnitude in MCE performance [32,34,42,49]. We can see that the present Cu18Al25Ho57 and Cu18Al25Tm57 amorphous ribbons can achieve the above criterion by adjusting the rare earth ratios only, which covers a 6–42 K wide temperature range. Considering the large −ΔSM with no thermal/magnetic hysteresis accompanied with considerable RC and RCP values indicate that the Cu18Al25Ho57 and Cu18Al25Tm57 amorphous ribbons are potential coolants for cryogenic application.
Fig. 7. The magnetic entropy change −ΔSM as a function of temperature for melt-spun Cu18Al25Ho57 (a) and Cu18Al25Tm57 (b) with the magnetic field changes from 0 to 1 to 0–7 T.
− (T − TC )/(Tr 1 − TC ); θ=⎧ ⎨ ⎩ (T − TC )/(Tr 2 − TC );
Materials
(6)
with f = 0.6 for the present study. Fig. 8 shows ΔS′ as a function of θ for both samples. It can be obviously note that the experimental data for different H distribute on one master curve, which verifies the magnetic phase transition of Cu18Al25Ho57 and Cu18Al25Tm57 ribbons is a second order. The factors of refrigerant capacity (RC) as well as the relative
3. Conclusions In short, two amorphousized Cu18Al25RE57 ribbons with RE of Ho and Tm were prepared successfully by a conventional melt-spinning technology, and a detailed of the GFA, magnetic and cryogenic MCE properties were studied. Both ribbons mentioned here undergo a typical PM to FM (second ordered) type transition, resulting in large MCEs in a wide temperature range. The MCE factors of −ΔSMmax, RC and RCP are 18.5 J kg−1 K−1, 368.0 and 484.9 J kg−1 for Cu18Al25RE57, as well as 18.2 J kg−1 K−1, 258.5 and 334.5 J kg−1 for Cu18Al25Tm57 under ΔH of 0–5 T, respectively. The similarly fascinating MCE performances together with near working temperatures make Cu18Al25RE57 amorphous ribbons competitive among active cryogenic MCE materials.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Fig. 8. Normalized magnetic entropy change (ΔS′ = ΔSM(T)/ΔSMmax) as a function of rescaled temperature (θ) at different ΔH for melt-spun Cu18Al25Ho57 (a) and Cu18Al25Tm57 (b) ribbons. 4
Journal of Magnetism and Magnetic Materials 495 (2020) 165888
Z. Dong and S. Yin
Acknowledgement
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