UC Irvine

Using neutron scattering techniques we have examined the magnetic transitions for compounds in the (Ho1-xErx)Rh4B4 pseudoternary system. We find a wide variety of behavior ranging from mean-field behavior for HoRh4B4 to complicated behavior with more than one type of ordering for Ho0.3Er0.7Rh4B4. Our results for the pseudoternary compounds are consistent with a model in which Ho orders along the c axis with nearly its free-ion moment, while ER orders in the basal plane, but with a moment reduced from the free-ion value. Ordering along the c axis results in the destruction of superconductivity in a sharp transition at the same temperature that a sharp spike appears in the heat capacity. Because Ho and Er have competing orthogonal magnetic anisotropies, pseudoternary compounds near the composition Ho0.3Er0.7Rh4B4 are near a multicritical point in the magnetic phase diagram. © 1982 The American Physical Society.