Magnetic interactions in ternary superconductors

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Abstract
Numerous ternary superconductors containing rare‐earth atoms have recently been studied in order to investigate the magnetic interactions between the conduction electrons and local magnetic moments. These investigations range from the evaluation of the strength of spin‐flip scattering of the conduction electrons off the rare‐earth moments to the problem of the coexistence of superconductivity and magnetic order. We present results of our studies on (Eu,Sn)Mo6S8, ErRh4B4, Er1−xHoxRh4B4 and Er1−xGdxRh4B4 using primarily the Mössbauer effect in 151Eu and 166Er, and nuclear magnetic resonance of 95Mo. The paramagnetic hyperfine spectra of the rare‐earth ions indicate a weak coupling of the 4f magnetic moment to the conduction electrons. The enhanced Hc2 value in (Eu,Sn)Mo6S8 is found to be related to a negative s‐band polarization at the Mo site. The magnetic moment on the Er atom in ErRh4B4 (and in related materials) in the magnetically ordered state is found to be about 8.3 μB. This is 30% larger than that measured from neutron diffraction studies, indicating that only a component of the moment shows long‐range magnetic order.