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Tuning of upper critical field anisotropy in Tb x Y 1 − x Ni…

2002; American Physical Society; Volume: 65; Issue: 22 Linguagem: Inglês

10.1103/physrevb.65.224416

1095-3795

H. Bitterlich, W. Löser, G. Behr, S.‐L. Drechsler, K. Nenkov, G. Fuchs, K.‐H. Müller, L. Schultz,

Iron-based superconductors research

The effect of paramagnetic Tb ions on the superconducting upper critical field ${H}_{c2}$ of ${\mathrm{Tb}}_{x}{\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{2}{\mathrm{B}}_{2}\mathrm{C}$ intermetallic compounds has been studied on bulk single crystals, which is an example of continuous tuning of anisotropic behavior of pseudoquaternary borocarbide compounds. With an increasing Tb content x both ${T}_{c}$ and the upper critical field ${H}_{c2}$ are reduced. Different from ${\mathrm{YNi}}_{2}{\mathrm{B}}_{2}\mathrm{C}$ a reversed large anisotropy ${H}_{c2}^{[001]}>{H}_{c2}^{[100]}$ is induced by the in-plane magnetic moments of the Tb ions, which is emphasized by the higher magnetization in the [100] direction. The magnitude of the anisotropy depends on the concentration x and the magnetic coupling between the Tb ions, and exhibits a maximum at $x=0.2.$ A theory is presented which explains the anisotropy of the upper critical field on the basis of magnetization measurements.