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The effect of oxygen and hydrogen on superconductivity and ferromagnetism in Eu1.5Ce0.5RuSr2Cu2O10
Physica B 280 (2000) 370}371
The e!ect of oxygen and hydrogen on superconductivity and ferromagnetism in Eu Ce RuSr Cu O I. Felner*, U. Asaf, Y. Levi, O. Millo Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
Abstract Eu Ce RuSr Cu O is the "rst Cu}O based material in which superconductivity (SC) and ferromagnetism (FM) have been shown to coexist (¹ "32 K, ¹ "122 K thus ¹ '¹ ). SC is con"ned to the CuO planes, and the ! + + ! magnetic ordering is due to the Ru sublattice. Hole doping in the CuO planes can be achieved with variation of oxygen or hydrogen concentrations. The e!ect of O is to increase ¹ (up to 49 K) and ¹ (up to 168 K). The e!ect of H is to ! + suppress SC and enhance the FM properties (¹ increases to 225 K). In contrast to other HTSC materials, this e!ect is + reversible: by depletion of hydrogen, SC is restored and ¹ drops back to 122 K. 2000 Elsevier Science B.V. All rights + reserved. PACS: 74.10.#V; 74.62.Bf; 75.50.Ee; 76.80.#y Keywords: High-temperature superconductors; Magnetism
Our as prepared (ASP) Eu Ce RuSr Cu O sample exhibits ferromagnetic (FM) order at ¹ "122 K and becomes SC at ¹ "32 K [1,2]. Hole + ! doping can be achieved with appropriate variation of the oxygen concentrations (P ), obtained by annealing the ASP sample at 9003C under O pressures up to 150 atm ¹ and ¹ depend strongly on P . On the other hand, ! + the e!ect of hydrogen is to degrade SC. ¹ is lowered ! with increasing H content, and ¹ increases up to 225 K. + Sample preparation and experimental details are described in Refs. [1,2]. Determination of absolute O content in all samples is di$cult [1,2] and we assume that the O content is around 10 [3]. XRD measurements indicate that within the instrumental accuracy all samples studied have similar lattice parameters [1,2]. As P increases from 0 (ASP) to 22, 75 and 150 atm, ¹ increases monotonically from 32(0.5) to 38, 46.5 and ! 49 K. Fig. 1 shows the normalized R(¹) for P "75 atm measured at various "elds. Above ¹ "46.5 K, a metal! lic behavior is observed. The derivative dR/d¹ at H"0 exhibits two broad peaks (with an area ratio of 3:1)
* Corresponding author. E-mail address: [email protected] (I. Felner)
indicating the existence of two major components, having ¹ of 32 and 45 K respectively, where the latter is ! below the percolation threshold. STS studies con"rm this "nding [4].
Fig. 1. The normalized resistivity measured under various applied magnetic "elds (in kOe) for Eu Ce RuSr Cu O sample annealed under 75 oxygen atm. Inset shows the derivative of R(¹) at H"0.
0921-4526/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 1 7 5 7 - 3
I. Felner et al. / Physica B 280 (2000) 370}371
Fig. 2. ZFC (open symbols) and FC (solid) susceptibility curves measured at 50 Oe. for samples annealed under 75 (circles) and 150 (triangles) oxygen atm. The curves for P "150 atm are extended in the inset.
Zero-"eld-cooled (ZFC) and "eld-cooled (FC) magnetic curves measured at 50 Oe, for samples annealed under P "75 and 150 atm are shown in Fig. 2. There are two contributions: (a) negative moments below ¹ due to the SC state of the Cu}O planes, and (b) ! positive moments which are contributed mainly by the FM state of the Ru sublattice. The curves merge around 168 K (inset), indicating the e!ect of oxygen on ¹ . + The ZFC branches for several hydrogen loaded samples measured at 30 Oe are shown in Fig. 3. The peak around 60 K for the ASP sample represents reorientation of the Ru moments where ¹ "122 K [1,2]. With in+ creasing H content, the peak position and ¹ value are + shifted to higher ¹. For H*0.14 at%, the peak is at 160 K and ¹ "225 K. ¹ is lowered with increasing + !
371
Fig. 3. ZFC susceptibility curves for various hydrogen loaded samples.
H concentration, and for H*0.14 the system is insulating. In contrast to other high-¹ materials, this behavior ! is reversible: by depletion of hydrogen, SC is restored and the ¹ values drop back to 122 K [1,2]. +
References [1] I. Felner, U. Asaf, Y. Levi, O. Millo, Phys. Rev. B 55 (1997) 3374. [2] I. Felner, U. Asaf, S.D. Goren, C. Korn, Phys. Rev. B 57 (1998) 550. [3] T.J. Goodwin, H.B. Radousky, R.N. Shelton, Physica C 204 (1992) 212. [4] Y. Levi, I. Felner, U. Asaf, O. Millo, Physica B, these Proceedings (LT-22).
The e!ect of oxygen and hydrogen on superconductivity and ferromagnetism in Eu Ce RuSr Cu O I. Felner*, U. Asaf, Y. Levi, O. Millo Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
Abstract Eu Ce RuSr Cu O is the "rst Cu}O based material in which superconductivity (SC) and ferromagnetism (FM) have been shown to coexist (¹ "32 K, ¹ "122 K thus ¹ '¹ ). SC is con"ned to the CuO planes, and the ! + + ! magnetic ordering is due to the Ru sublattice. Hole doping in the CuO planes can be achieved with variation of oxygen or hydrogen concentrations. The e!ect of O is to increase ¹ (up to 49 K) and ¹ (up to 168 K). The e!ect of H is to ! + suppress SC and enhance the FM properties (¹ increases to 225 K). In contrast to other HTSC materials, this e!ect is + reversible: by depletion of hydrogen, SC is restored and ¹ drops back to 122 K. 2000 Elsevier Science B.V. All rights + reserved. PACS: 74.10.#V; 74.62.Bf; 75.50.Ee; 76.80.#y Keywords: High-temperature superconductors; Magnetism
Our as prepared (ASP) Eu Ce RuSr Cu O sample exhibits ferromagnetic (FM) order at ¹ "122 K and becomes SC at ¹ "32 K [1,2]. Hole + ! doping can be achieved with appropriate variation of the oxygen concentrations (P ), obtained by annealing the ASP sample at 9003C under O pressures up to 150 atm ¹ and ¹ depend strongly on P . On the other hand, ! + the e!ect of hydrogen is to degrade SC. ¹ is lowered ! with increasing H content, and ¹ increases up to 225 K. + Sample preparation and experimental details are described in Refs. [1,2]. Determination of absolute O content in all samples is di$cult [1,2] and we assume that the O content is around 10 [3]. XRD measurements indicate that within the instrumental accuracy all samples studied have similar lattice parameters [1,2]. As P increases from 0 (ASP) to 22, 75 and 150 atm, ¹ increases monotonically from 32(0.5) to 38, 46.5 and ! 49 K. Fig. 1 shows the normalized R(¹) for P "75 atm measured at various "elds. Above ¹ "46.5 K, a metal! lic behavior is observed. The derivative dR/d¹ at H"0 exhibits two broad peaks (with an area ratio of 3:1)
* Corresponding author. E-mail address: [email protected] (I. Felner)
indicating the existence of two major components, having ¹ of 32 and 45 K respectively, where the latter is ! below the percolation threshold. STS studies con"rm this "nding [4].
Fig. 1. The normalized resistivity measured under various applied magnetic "elds (in kOe) for Eu Ce RuSr Cu O sample annealed under 75 oxygen atm. Inset shows the derivative of R(¹) at H"0.
0921-4526/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 1 7 5 7 - 3
I. Felner et al. / Physica B 280 (2000) 370}371
Fig. 2. ZFC (open symbols) and FC (solid) susceptibility curves measured at 50 Oe. for samples annealed under 75 (circles) and 150 (triangles) oxygen atm. The curves for P "150 atm are extended in the inset.
Zero-"eld-cooled (ZFC) and "eld-cooled (FC) magnetic curves measured at 50 Oe, for samples annealed under P "75 and 150 atm are shown in Fig. 2. There are two contributions: (a) negative moments below ¹ due to the SC state of the Cu}O planes, and (b) ! positive moments which are contributed mainly by the FM state of the Ru sublattice. The curves merge around 168 K (inset), indicating the e!ect of oxygen on ¹ . + The ZFC branches for several hydrogen loaded samples measured at 30 Oe are shown in Fig. 3. The peak around 60 K for the ASP sample represents reorientation of the Ru moments where ¹ "122 K [1,2]. With in+ creasing H content, the peak position and ¹ value are + shifted to higher ¹. For H*0.14 at%, the peak is at 160 K and ¹ "225 K. ¹ is lowered with increasing + !
371
Fig. 3. ZFC susceptibility curves for various hydrogen loaded samples.
H concentration, and for H*0.14 the system is insulating. In contrast to other high-¹ materials, this behavior ! is reversible: by depletion of hydrogen, SC is restored and the ¹ values drop back to 122 K [1,2]. +
References [1] I. Felner, U. Asaf, Y. Levi, O. Millo, Phys. Rev. B 55 (1997) 3374. [2] I. Felner, U. Asaf, S.D. Goren, C. Korn, Phys. Rev. B 57 (1998) 550. [3] T.J. Goodwin, H.B. Radousky, R.N. Shelton, Physica C 204 (1992) 212. [4] Y. Levi, I. Felner, U. Asaf, O. Millo, Physica B, these Proceedings (LT-22).