Magnetic and superconducting properties of single-crystal TmNi2 B2C

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Cho, B. K.
Xu, Ming
Miller, L. L.
Johnston, D. C.
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American Physical Society
Canfield, Paul
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The temperature (T) and applied magnetic field (H) dependent magnetization has been measured for a single crystal of TmNi2B2C in order to study the interplay of superconductivity and the magnetism of the Tm sublattice. The normal-state magnetization of TmNi2B2C is anisotropic from 2 to 300 K with the magnetic field applied normal to the c axis (H perpendicular to c) leading to a smaller induced magnetization than the magnetization for the magnetic field applied parallel to the c axis (H parallel to c). This anisotropy is attributed to crystalline electric field (CEF) splitting of the J=6 manifold of the Tm+3 ion. From the inverse susceptibility [1/chi(T)] for H parallel to c and H perpendicular to c, the CEF parameter, B-2(0), is found to be (-1.15+/-0.02) K. The superconducting state magnetization for H approximate to H-c2(T) obeys the Ginzburg-Landau theory which is used to evaluate the upper critical magnetic field H-c2(T) and dH(c2)/dT\T-c values. The superconducting properties in this temperature region are similar to those of the nonmagnetic superconductor YNi2B2C, which has been shown to be an isotropic conventional type-II superconductor. For T less than or equal to 6 K, H-c2(T) shows highly anisotropic behavior: H(c2)(perpendicular to c)approximate to 2H(c2)(parallel to c). For both H parallel to c and H perpendicular to c, H-c2(T) reaches a broad maximum near 4 K and decreases as T approaches T-N=(1.52+/-0.05) K, indicating the interplay between superconductivity and magnetism. The broad maximum in H-c2( T) of TmNi2B2C is likely a result of the increasing Tm sublattice magnetization at H-c2(T) with decreasing temperature, rather than of antiferromagnetic fluctuations.
This article is published as Cho, B. K., Ming Xu, P. C. Canfield, L. L. Miller, and D. C. Johnston. "Magnetic and superconducting properties of single-crystal TmNi 2 B 2 C." Physical Review B 52, no. 5 (1995): 3676. DOI: 10.1103/PhysRevB.52.3676 Copyright 1995 American Physical Society. Posted with permission.