- Email: [email protected]
Antiferromagnetic versus spin-glass like behavior in MnIn2S4
ARTICLE IN PRESS
Journal of Magnetism and Magnetic Materials 312 (2007) 294–297 www.elsevier.com/locate/jmmm
Antiferromagnetic versus spin-glass like behavior in MnIn2S4 V. Sagredoa,, M.C. Moro´nb, L. Betancourta, G.E. Delgadoc a
Laboratorio de Magnetismo, Departamento de Fı´sica, Facultad de Ciencias, Universidad de los Andes, Me´rida, Venezuela b Instituto de Ciencia de Materiales de Arago´n, C.S.I.C.—Universidad de Zaragoza, E-50009, Zaragoza, Spain c Laboratorio de Cristalografı´a, Departamento de Quı´mica, Facultad de Ciencias, Universidad de los Andes, Me´rida, Venezuela Received 12 April 2006; received in revised form 6 October 2006 Available online 14 November 2006
Abstract The low-temperature magnetic properties of MnIn2S4 have been studied using AC magnetic susceptibility and magnetization experiments. High-temperature susceptibility fits indicate the presence of antiferromagnetic interactions. Low-field magnetization data show a peak at 5.670.1 K, below which strong irreversibility is observed between zero-field-cooled (ZFC) and field-cooled (FC) cycles suggesting that the observed peak corresponds to a spin-glass-like transition instead of the antiferromagnetic one previously reported. Further evidence of this magnetic state comes from AC susceptibility data at different frequencies. The in-phase component w0 (T) exhibits the behavior expected of spin glasses, i.e. a shift of the cusp to higher temperatures for higher frequencies. r 2006 Elsevier B.V. All rights reserved. PACS: 75.50 Lk; 81.10.h; 75.59Pp Keywords: Semimagnetic semiconductor; Spin glass; Spinel
1. Introduction Among spin glasses, a great deal of continuing interest has been dedicated to materials with spinel structure. This is essentially related to the existence of two types of crystallographic sub-lattices: one corresponding to the tetrahedral and the other to the octahedral sites [1]. This lattice presents a great flexibility in hosting various metal ions AIn2S4 (A: Mn, Fe, Ni) with different degrees of positional disorder giving rise to a disorder in the distribution of the magnetic exchange interactions. Depending on their distribution and their sign, different magnetic behaviors have been observed: spin glass in FeIn2S4 [2], antiferromagnetic in MnIn2S4 [3] and paramagnetic in NiIn2S4 [4] at the measured temperatures. In more recent works [5,6], interest has been given to the magnetic properties of the MnIn2X4 (X: S; Se; Te) system. Thus for the selenide and telluride compounds, a spin-glass behavior was reported with freezing temperature of 3.52 and 3.8 K, respectively. However, Hsu et al. [3] reported a Corresponding author. Tel.: +58 274 2401342; fax: +58 274 2401365.
E-mail address: [email protected] (V. Sagredo). 0304-8853/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2006.10.609
classical antiferromagnetic behavior for the sulfide compound MnIn2S4 with Ne`el temperature TN ¼ 4.9 K. Interestingly enough, the crystal structure of this material [7] exhibits a disordered distribution of magnetic ions. This disordered distribution would suggest a glassy-type magnetic behavior, as the one published for MnIn2Se4 and MnIn2Te4, better than the classical antiferromagnetic one, as previously reported. Considering that the field of random magnetism has an important actual interest, we focus our study in the interaction between the magnetic and the structural properties of MnIn2S4. In particular, we are interested in determining if this material is a classical anti-ferromagnet or, on the contrary, its magnetic properties at low temperature can be better described by a glassytype behavior, as probably expected from the disordered distribution of the magnetic ions that MnIn2S4 exhibits [7]. 2. Experimental procedure Small/twinned crystals of MnIn2S4 have been grown by chemical vapor transport in a closed quartz tube using I2 as the transport agent. The crystals were octahedrally shaped and had a dark red color.
ARTICLE IN PRESS V. Sagredo et al. / Journal of Magnetism and Magnetic Materials 312 (2007) 294–297
120
100
1/X (Oe-mol/emu)
DC magnetization measurements were performed on crushed crystals of MnIn2S4 compound by using a quantum design SQUID magnetometer. Measurements were made for fields between 50 and 1300 Oe in both zerofield-cooled (ZFC) and field-cooled (FC) modes between 1.8 and 300 K. AC magnetic susceptibility measurements as a function of the temperature were made at low AC driving field with frequencies ranging between 1 and 1000 Hz. X-ray powder diffraction pattern (XRD) was obtained at room temperature by using a Siemens D5005 diffractometer, with a Bragg–Brentano geometry in y/y reflection mode and CuKa radiation (l ¼ 1.54059 A˚). Data were collected by steps of 0.021 (2y) over the angular range of 10–1001, with a counting time of 50 s per step.
295
80
60
40 MnIn2S4 H =100Oe
20
3. Results and discussion
0
The experimental magnetization, measured in the FC and ZFC mode, is shown in Fig. 1 as a function of the temperature at 50 Oe. This result shows a peak in the ZFC data at about 5.670.1 K, whereas the FC data displays a small hump at this temperature. It is also possible to observe that the FC and ZFC curves present a clear irreversibility below 5.6 K, suggesting that the magnetic state below that temperature could be of a spin-glass-like type. The high-temperature (TX100 K) data of the inverse susceptibility w1 DC can be well fitted with the Curie–Weiss law as is shown in Fig. 2. The value of the Curie–Weiss temperature y ¼ 12473 K is negative, indicating predominant antiferromagnetic interactions between the Mn ions with an effective magnetic moment, meff ¼ 5.837 9.0 1300 Oe
FC ZFC FC
7.0 M (arbitrary units)
400 Oe ZFC 5.0
FC 50 Oe
3.0
ZFC MnIn2S4
1.0 1
2
3
4
5
6
7
8
9
T (K) Fig. 1. Temperature dependence of the ZFC and FC magnetization at three different magnetic fields (50, 400 and 1300 Oe) for MnIn2S4.
0
50
100
150
200
250
300
350
T (K) Fig. 2. Temperature dependence of the inverse of the DC magnetic susceptibility for MnIn2S4. The straight line corresponds to the linear fit to the high-temperature data (T4100 K).
0.05 mB, similar to that reported in MnIn2Te4 [6] and MnIn2Se4 [5]. This effective moment is slightly smaller than the expected spin-only value for Mn2+ (meff ¼ 5.92 mB with S ¼ 52). The large deviation from the Curie–Weiss behavior shown in Fig. 2 is due to strong dominant antiferromagnetic interactions between Mn ions [6]. It is interesting to note that the y value is more than one order of magnitude larger than Tf, i.e., y/TfE25. This high y/Tf value is consistent with the existence of magnetic frustration expected for a spin-glass system. Further evidence of such magnetic behavior was found in the AC magnetic susceptibility experiments performed as a function of the temperature and frequency (see Fig. 3). It is possible to observe a clear peak in the real component w0 (T) of the AC susceptibility. It can also be noted that the peak shifts to higher temperatures for higher applied frequencies i.e. from Tf ¼ 5.8070.05 K for f ¼ 1 Hz to Tf ¼ 5.9570.05 K for f ¼ 1000 Hz. This frequency dependence is also compatible with a spin-glass-like behavior. The increase, at low temperature, of the imaginary part w00 (T) is also in good agreement with the existence of such a magnetic behavior. The frecuency-dependent curves overlap at temperatures TX6 K indicating that the system is in thermodynamic equilibrium [8]. In addition to the frequency dependence of Tf in wAC ðT Þ discussed above, the irreversibility between the ZFC and FC modes observed at 50 Oe was also observed, as shown in Fig. 1, at different magnetic fields. This behavior is similar to what is reported in other spin-glass systems [9–11] reinforcing the assumption of the spin-glass-like behavior. MnIn2S4 has been previously reported to exhibit
ARTICLE IN PRESS V. Sagredo et al. / Journal of Magnetism and Magnetic Materials 312 (2007) 294–297
296
0.13
22000
0.010
19000
X'
X'
5 0.10
1 Hz 10 Hz 117 Hz 499 Hz 997 Hz
5.4 5.8 6.2 T (K)
0.004
0.002
Intensity (counts)
X"
0.11
X'' ( arbitrary units )
X' ( arbitrary units )
0.12 0.006
MnIn2S4
13000 10000 7000 4000 1000
-2800
0.000
-6000 10
X'"
MnIn2S4
20
30
40
1
2
3
4
5
50
60
70
80
90
100
2 Theta (°)
0.09 0
Yobs Ycalc Yobs-Ycalc Bragg_position
16000
0.008
6
7
8
T ( K)
Fig. 4. Final Rietveld refinement plot for MnIn2S4. The lower trace is the difference curve between the observed and calculated patterns. The Bragg reflections are indicated by vertical bars.
Fig. 3. Temperature dependence of the AC-susceptibility taken at different frequencies.
a maximum in the magnetic DC susceptibility at 4.9 K and a negative Curie–Weiss temperature [3]. Hsu et al. [3], in the absence of additional susceptibility and magnetization measurements, have interpreted these experimental data as a classical antiferromagnetic ordering below 4.9 K. However, a maximum in the evolution of the DC susceptibility versus temperature is also compatible with a spin-glass behavior [6]. XRD experiments were carried out in order to check the stoichiometry of the sample and to determine the arrangement of the cations in the lattice structure. The X-ray data show a single phase. Structural studies, including the cation distribution, were performed by the Rietveld refinement method [12] using the FULLPROF program [13]. Atomic coordinates reported by Lutz et al. [7] were used as a starting model. The final refinement involved the following 18 parameters: zero shift, scale factor, two asymmetry parameters, five coefficients to define the functional angular variation of the background, three peak half-width parameters U, V, W, and a mixing parameter of the pseudo-Voigt peak-shape function, one unit cell parameter, one positional parameter (x for anion), two occupational factors and one overall isotropic temperature factor. The final figures of merit were: Rp ¼ 6.1%, Rwp ¼ 7.8%, Rexp ¼ 6.7%, S ¼ 1.2 and w2 ¼ 1.4, for 4501 step intensities and 45 independent reflections. The definitions of these figures were taken from Ref. [12]. The observed, calculated and difference profile for the final refinement are shown in Fig. 4. Atomic coordinates, isotropic temperature factors and relevant geometric data for MnIn2S4 are listed in Table 1. MnIn2S4 is a spinel-type compound and crystallizes in the space group Fd3m. In this structure the Mn1 and In1 cations share the tetrahedral, whereas the Mn2 and In2 cations share the octahedral sites. The chemical composi-
Table 1 Unit cell parameters, atomic coordinates, isotropic temperature factor, occupancy factors and bond distances for MnIn2S4 derived from the Rietveld refinement Atom Site
x
y
z
foc
B (A˚2)
Space group Fd3 m , Z ¼ 8, a ¼ 10.7225(2) A˚, V ¼ 1232.79(4) A˚3 1 1 1 Mn(1) 8a 0.66(8) 0.92(6) 8 8 8 In(1) 0.34(8) 0.92(6) 1 1 1 0.16(4) 0.92(6) Mn(2) 16d 2 2 2 In(2) 0.84(4) 0.92(6) S 32e 0.2573(3) 0.2573(3) 0.2573(3) 1 0.92(6) d(8a–S) 2.457(3) (A˚)
d(16d–S) 2.605(3) (A˚)
tion of the material was tested by the refinement of the occupancy factors of both Mn and In atoms (see Table 1). A good agreement was found with the nominal composition. Rietveld analysis clearly shows a disordered distribution of the Mn and In cations in both the octahedral and tetrahedral sites (see Table 1). This disordered distribution of the magnetic ions in the sample under study (see Table 1) is compatible with the existence of a spin-glass-like phase at low temperatures. 4. Conclusions We can conclude that although MnIn2S4 was reported to order as a classical antiferromagnet at low temperature, the present study, based on the evolution with the temperature (i) of the ZFC and FC magnetization at different magnetic fields, and (ii) of the AC magnetic susceptibility at various frequencies, confirms the presence of a spin-glass-like phase at low temperature. This result is in good agreement with the random distribution of the magnetic ions in the crystal lattice and the presence of magnetic frustration reflected by the high y/Tf relation.
ARTICLE IN PRESS V. Sagredo et al. / Journal of Magnetism and Magnetic Materials 312 (2007) 294–297
Acknowledgments We wish to thank CDCHT-ULA (Grant C-1395-06-05B) and FONACIT (Grant LAB-97000821), the Spanish Government and the Diputacio´n General de Arago´n for research grants MAT2004-03395-C02-01 and DGA2005E16, respectively. References [1] E. Agostinelli, D. Fiorani, A.M. Testa, Fundamental and Applicative Aspect of Disordered Magnetism, World Scientific Publ. Co., Singapore, 1988, p. 30. [2] M. Eibchuz, E. Hermon, S. Shtrikman, Solid State Commun. 5 (1967) 529. [3] C.-I. Hsu, J. Steger, E. DeMeo, A. Wold, G. Heller, J. Solid State Chem. 13 (1975) 304.
297
[4] J. Alvarez, V. Sagredo, J. Mantilla, J. Magn. Magn. Mater. 196–197 (1999) 407. [5] J.C. Mantilla, V. Bindilatti, E. ter Haar, J. Coaquira, J.G. de Souza, G.X. Grantens, V. Sagredo, J. Magn. Magn. Mater. 272–276 (2004) 1308. [6] G. Goya, V. Sagredo, Phys. Rev. B 64 (2001) 235208. [7] H. Lutz, M.Z. Jung, Z. Anorg. Allg. Chem. 579 (1989) 57. [8] J. Spalek, A. Lewicki, Z. Tarnawski, J.K. Furdyna, R.R. Galazka, Z. Obuszko, Phys. Rev. B 33 (1986) 3407. [9] J.A. Mydosh, 1993. Spin Glasses: an experimental introduction Taylor and Francis, London (Chapter 3). [10] G.A. Goya, A. Memo, H. Haeuseler, J. Solid State Chem. 164 (2002) 326. [11] M.C. Moro´n, J. Campo, F. Palacio, G. Attolini, C. Pelosi, J. Magn. Magn. Mater. 196–197 (1999) 437. [12] H.M. Rietveld, J. Appl. Crystallogr. 2 (1969) 65. [13] Rodriguez-Carvajal J, Fullprof (version 2.80, July 2004), Laboratoire Le´on Brillouin (CEA-CNRS), France.
Journal of Magnetism and Magnetic Materials 312 (2007) 294–297 www.elsevier.com/locate/jmmm
Antiferromagnetic versus spin-glass like behavior in MnIn2S4 V. Sagredoa,, M.C. Moro´nb, L. Betancourta, G.E. Delgadoc a
Laboratorio de Magnetismo, Departamento de Fı´sica, Facultad de Ciencias, Universidad de los Andes, Me´rida, Venezuela b Instituto de Ciencia de Materiales de Arago´n, C.S.I.C.—Universidad de Zaragoza, E-50009, Zaragoza, Spain c Laboratorio de Cristalografı´a, Departamento de Quı´mica, Facultad de Ciencias, Universidad de los Andes, Me´rida, Venezuela Received 12 April 2006; received in revised form 6 October 2006 Available online 14 November 2006
Abstract The low-temperature magnetic properties of MnIn2S4 have been studied using AC magnetic susceptibility and magnetization experiments. High-temperature susceptibility fits indicate the presence of antiferromagnetic interactions. Low-field magnetization data show a peak at 5.670.1 K, below which strong irreversibility is observed between zero-field-cooled (ZFC) and field-cooled (FC) cycles suggesting that the observed peak corresponds to a spin-glass-like transition instead of the antiferromagnetic one previously reported. Further evidence of this magnetic state comes from AC susceptibility data at different frequencies. The in-phase component w0 (T) exhibits the behavior expected of spin glasses, i.e. a shift of the cusp to higher temperatures for higher frequencies. r 2006 Elsevier B.V. All rights reserved. PACS: 75.50 Lk; 81.10.h; 75.59Pp Keywords: Semimagnetic semiconductor; Spin glass; Spinel
1. Introduction Among spin glasses, a great deal of continuing interest has been dedicated to materials with spinel structure. This is essentially related to the existence of two types of crystallographic sub-lattices: one corresponding to the tetrahedral and the other to the octahedral sites [1]. This lattice presents a great flexibility in hosting various metal ions AIn2S4 (A: Mn, Fe, Ni) with different degrees of positional disorder giving rise to a disorder in the distribution of the magnetic exchange interactions. Depending on their distribution and their sign, different magnetic behaviors have been observed: spin glass in FeIn2S4 [2], antiferromagnetic in MnIn2S4 [3] and paramagnetic in NiIn2S4 [4] at the measured temperatures. In more recent works [5,6], interest has been given to the magnetic properties of the MnIn2X4 (X: S; Se; Te) system. Thus for the selenide and telluride compounds, a spin-glass behavior was reported with freezing temperature of 3.52 and 3.8 K, respectively. However, Hsu et al. [3] reported a Corresponding author. Tel.: +58 274 2401342; fax: +58 274 2401365.
E-mail address: [email protected] (V. Sagredo). 0304-8853/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2006.10.609
classical antiferromagnetic behavior for the sulfide compound MnIn2S4 with Ne`el temperature TN ¼ 4.9 K. Interestingly enough, the crystal structure of this material [7] exhibits a disordered distribution of magnetic ions. This disordered distribution would suggest a glassy-type magnetic behavior, as the one published for MnIn2Se4 and MnIn2Te4, better than the classical antiferromagnetic one, as previously reported. Considering that the field of random magnetism has an important actual interest, we focus our study in the interaction between the magnetic and the structural properties of MnIn2S4. In particular, we are interested in determining if this material is a classical anti-ferromagnet or, on the contrary, its magnetic properties at low temperature can be better described by a glassytype behavior, as probably expected from the disordered distribution of the magnetic ions that MnIn2S4 exhibits [7]. 2. Experimental procedure Small/twinned crystals of MnIn2S4 have been grown by chemical vapor transport in a closed quartz tube using I2 as the transport agent. The crystals were octahedrally shaped and had a dark red color.
ARTICLE IN PRESS V. Sagredo et al. / Journal of Magnetism and Magnetic Materials 312 (2007) 294–297
120
100
1/X (Oe-mol/emu)
DC magnetization measurements were performed on crushed crystals of MnIn2S4 compound by using a quantum design SQUID magnetometer. Measurements were made for fields between 50 and 1300 Oe in both zerofield-cooled (ZFC) and field-cooled (FC) modes between 1.8 and 300 K. AC magnetic susceptibility measurements as a function of the temperature were made at low AC driving field with frequencies ranging between 1 and 1000 Hz. X-ray powder diffraction pattern (XRD) was obtained at room temperature by using a Siemens D5005 diffractometer, with a Bragg–Brentano geometry in y/y reflection mode and CuKa radiation (l ¼ 1.54059 A˚). Data were collected by steps of 0.021 (2y) over the angular range of 10–1001, with a counting time of 50 s per step.
295
80
60
40 MnIn2S4 H =100Oe
20
3. Results and discussion
0
The experimental magnetization, measured in the FC and ZFC mode, is shown in Fig. 1 as a function of the temperature at 50 Oe. This result shows a peak in the ZFC data at about 5.670.1 K, whereas the FC data displays a small hump at this temperature. It is also possible to observe that the FC and ZFC curves present a clear irreversibility below 5.6 K, suggesting that the magnetic state below that temperature could be of a spin-glass-like type. The high-temperature (TX100 K) data of the inverse susceptibility w1 DC can be well fitted with the Curie–Weiss law as is shown in Fig. 2. The value of the Curie–Weiss temperature y ¼ 12473 K is negative, indicating predominant antiferromagnetic interactions between the Mn ions with an effective magnetic moment, meff ¼ 5.837 9.0 1300 Oe
FC ZFC FC
7.0 M (arbitrary units)
400 Oe ZFC 5.0
FC 50 Oe
3.0
ZFC MnIn2S4
1.0 1
2
3
4
5
6
7
8
9
T (K) Fig. 1. Temperature dependence of the ZFC and FC magnetization at three different magnetic fields (50, 400 and 1300 Oe) for MnIn2S4.
0
50
100
150
200
250
300
350
T (K) Fig. 2. Temperature dependence of the inverse of the DC magnetic susceptibility for MnIn2S4. The straight line corresponds to the linear fit to the high-temperature data (T4100 K).
0.05 mB, similar to that reported in MnIn2Te4 [6] and MnIn2Se4 [5]. This effective moment is slightly smaller than the expected spin-only value for Mn2+ (meff ¼ 5.92 mB with S ¼ 52). The large deviation from the Curie–Weiss behavior shown in Fig. 2 is due to strong dominant antiferromagnetic interactions between Mn ions [6]. It is interesting to note that the y value is more than one order of magnitude larger than Tf, i.e., y/TfE25. This high y/Tf value is consistent with the existence of magnetic frustration expected for a spin-glass system. Further evidence of such magnetic behavior was found in the AC magnetic susceptibility experiments performed as a function of the temperature and frequency (see Fig. 3). It is possible to observe a clear peak in the real component w0 (T) of the AC susceptibility. It can also be noted that the peak shifts to higher temperatures for higher applied frequencies i.e. from Tf ¼ 5.8070.05 K for f ¼ 1 Hz to Tf ¼ 5.9570.05 K for f ¼ 1000 Hz. This frequency dependence is also compatible with a spin-glass-like behavior. The increase, at low temperature, of the imaginary part w00 (T) is also in good agreement with the existence of such a magnetic behavior. The frecuency-dependent curves overlap at temperatures TX6 K indicating that the system is in thermodynamic equilibrium [8]. In addition to the frequency dependence of Tf in wAC ðT Þ discussed above, the irreversibility between the ZFC and FC modes observed at 50 Oe was also observed, as shown in Fig. 1, at different magnetic fields. This behavior is similar to what is reported in other spin-glass systems [9–11] reinforcing the assumption of the spin-glass-like behavior. MnIn2S4 has been previously reported to exhibit
ARTICLE IN PRESS V. Sagredo et al. / Journal of Magnetism and Magnetic Materials 312 (2007) 294–297
296
0.13
22000
0.010
19000
X'
X'
5 0.10
1 Hz 10 Hz 117 Hz 499 Hz 997 Hz
5.4 5.8 6.2 T (K)
0.004
0.002
Intensity (counts)
X"
0.11
X'' ( arbitrary units )
X' ( arbitrary units )
0.12 0.006
MnIn2S4
13000 10000 7000 4000 1000
-2800
0.000
-6000 10
X'"
MnIn2S4
20
30
40
1
2
3
4
5
50
60
70
80
90
100
2 Theta (°)
0.09 0
Yobs Ycalc Yobs-Ycalc Bragg_position
16000
0.008
6
7
8
T ( K)
Fig. 4. Final Rietveld refinement plot for MnIn2S4. The lower trace is the difference curve between the observed and calculated patterns. The Bragg reflections are indicated by vertical bars.
Fig. 3. Temperature dependence of the AC-susceptibility taken at different frequencies.
a maximum in the magnetic DC susceptibility at 4.9 K and a negative Curie–Weiss temperature [3]. Hsu et al. [3], in the absence of additional susceptibility and magnetization measurements, have interpreted these experimental data as a classical antiferromagnetic ordering below 4.9 K. However, a maximum in the evolution of the DC susceptibility versus temperature is also compatible with a spin-glass behavior [6]. XRD experiments were carried out in order to check the stoichiometry of the sample and to determine the arrangement of the cations in the lattice structure. The X-ray data show a single phase. Structural studies, including the cation distribution, were performed by the Rietveld refinement method [12] using the FULLPROF program [13]. Atomic coordinates reported by Lutz et al. [7] were used as a starting model. The final refinement involved the following 18 parameters: zero shift, scale factor, two asymmetry parameters, five coefficients to define the functional angular variation of the background, three peak half-width parameters U, V, W, and a mixing parameter of the pseudo-Voigt peak-shape function, one unit cell parameter, one positional parameter (x for anion), two occupational factors and one overall isotropic temperature factor. The final figures of merit were: Rp ¼ 6.1%, Rwp ¼ 7.8%, Rexp ¼ 6.7%, S ¼ 1.2 and w2 ¼ 1.4, for 4501 step intensities and 45 independent reflections. The definitions of these figures were taken from Ref. [12]. The observed, calculated and difference profile for the final refinement are shown in Fig. 4. Atomic coordinates, isotropic temperature factors and relevant geometric data for MnIn2S4 are listed in Table 1. MnIn2S4 is a spinel-type compound and crystallizes in the space group Fd3m. In this structure the Mn1 and In1 cations share the tetrahedral, whereas the Mn2 and In2 cations share the octahedral sites. The chemical composi-
Table 1 Unit cell parameters, atomic coordinates, isotropic temperature factor, occupancy factors and bond distances for MnIn2S4 derived from the Rietveld refinement Atom Site
x
y
z
foc
B (A˚2)
Space group Fd3 m , Z ¼ 8, a ¼ 10.7225(2) A˚, V ¼ 1232.79(4) A˚3 1 1 1 Mn(1) 8a 0.66(8) 0.92(6) 8 8 8 In(1) 0.34(8) 0.92(6) 1 1 1 0.16(4) 0.92(6) Mn(2) 16d 2 2 2 In(2) 0.84(4) 0.92(6) S 32e 0.2573(3) 0.2573(3) 0.2573(3) 1 0.92(6) d(8a–S) 2.457(3) (A˚)
d(16d–S) 2.605(3) (A˚)
tion of the material was tested by the refinement of the occupancy factors of both Mn and In atoms (see Table 1). A good agreement was found with the nominal composition. Rietveld analysis clearly shows a disordered distribution of the Mn and In cations in both the octahedral and tetrahedral sites (see Table 1). This disordered distribution of the magnetic ions in the sample under study (see Table 1) is compatible with the existence of a spin-glass-like phase at low temperatures. 4. Conclusions We can conclude that although MnIn2S4 was reported to order as a classical antiferromagnet at low temperature, the present study, based on the evolution with the temperature (i) of the ZFC and FC magnetization at different magnetic fields, and (ii) of the AC magnetic susceptibility at various frequencies, confirms the presence of a spin-glass-like phase at low temperature. This result is in good agreement with the random distribution of the magnetic ions in the crystal lattice and the presence of magnetic frustration reflected by the high y/Tf relation.
ARTICLE IN PRESS V. Sagredo et al. / Journal of Magnetism and Magnetic Materials 312 (2007) 294–297
Acknowledgments We wish to thank CDCHT-ULA (Grant C-1395-06-05B) and FONACIT (Grant LAB-97000821), the Spanish Government and the Diputacio´n General de Arago´n for research grants MAT2004-03395-C02-01 and DGA2005E16, respectively. References [1] E. Agostinelli, D. Fiorani, A.M. Testa, Fundamental and Applicative Aspect of Disordered Magnetism, World Scientific Publ. Co., Singapore, 1988, p. 30. [2] M. Eibchuz, E. Hermon, S. Shtrikman, Solid State Commun. 5 (1967) 529. [3] C.-I. Hsu, J. Steger, E. DeMeo, A. Wold, G. Heller, J. Solid State Chem. 13 (1975) 304.
297
[4] J. Alvarez, V. Sagredo, J. Mantilla, J. Magn. Magn. Mater. 196–197 (1999) 407. [5] J.C. Mantilla, V. Bindilatti, E. ter Haar, J. Coaquira, J.G. de Souza, G.X. Grantens, V. Sagredo, J. Magn. Magn. Mater. 272–276 (2004) 1308. [6] G. Goya, V. Sagredo, Phys. Rev. B 64 (2001) 235208. [7] H. Lutz, M.Z. Jung, Z. Anorg. Allg. Chem. 579 (1989) 57. [8] J. Spalek, A. Lewicki, Z. Tarnawski, J.K. Furdyna, R.R. Galazka, Z. Obuszko, Phys. Rev. B 33 (1986) 3407. [9] J.A. Mydosh, 1993. Spin Glasses: an experimental introduction Taylor and Francis, London (Chapter 3). [10] G.A. Goya, A. Memo, H. Haeuseler, J. Solid State Chem. 164 (2002) 326. [11] M.C. Moro´n, J. Campo, F. Palacio, G. Attolini, C. Pelosi, J. Magn. Magn. Mater. 196–197 (1999) 437. [12] H.M. Rietveld, J. Appl. Crystallogr. 2 (1969) 65. [13] Rodriguez-Carvajal J, Fullprof (version 2.80, July 2004), Laboratoire Le´on Brillouin (CEA-CNRS), France.