Magnetic anisotropy and transitions in single crystals of RCo_2Ge_2
Abstract
Thermodynamic, transport, magnetization, and x-ray diffraction measurements were used to characterize single crystals of the tetragonal RCo_2Ge2 series, where R = Y, La-Nd, Sm-Tm. Series members with Y, La, and Ce are Pauli-paramagnetic, which is consistent with the Co being nonmagnetic. Members with Gd and (divalent) Eu are magnetically isotropic, due to their S ground state. The Sm compound is slightly anisotropic. All other members of the series have very anisotropic local moments, due to the tetragonal crystal field, which splits the Hund's-rule ground state. The moments of Er and Tm are strongly planar, while those of Pr, Nd, Tb, Dy, and Ho are strongly axial; the Stevens coefficient B_2^0 has been measured for all these series members. All local moment series members undergo antiferromagnetic transitions with relatively high Néel temperatures, ranging from 2.2 K for Tm to 32.8 K for Gd and Tb. Néel temperatures of series members with heavy rare earths roughly scale with the de Gennes parameter, with tetragonal corrections, whereas the Néel temperatures of series members with light rare earths do not de Gennes-scale. Many members of this series have what appears to be a second magnetic transition below their Néel temperatures. Some of these transitions are evident in heat capacity data, while others are not.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2002
- Bibcode:
- 2002APS..MARF17001C