Magnetic domains and anisotropy in single crystals of Er(Co,Mn)O3

We have previously reported the magnetic properties of the Er(Co,Mn)O₃ solid solution, in which Mn atoms have been partially substituted by Co. Several magnetic entities coexist in this system (Er³⁺, Mn³⁺, Mn⁴⁺, Co²⁺, Co³⁺), resulting into a subtle interplay between different interactions and leading to unusual phenomena such as: a spin reversal due to antiferromagnetic exchange between erbium and transition-metal spins, a step-like transition due to reorientation of magnetic domains, a relaxation mechanism connected to the rotation energy of the domains, the intersection of the increasing and decreasing branches in the magnetization loops, etc. These results have been obtained in highly dense ceramic samples for compositions near ErCo_0.50Mn_0.50O₃. In order to better understand the different mechanisms, we have started a program on crystal growth. High-quality single crystals of orthorhombic structure (S.G. Pbnm) of Er(Co,Mn)O₃ manganite were grown in a floating-zone oven under oxygen atmosphere. Although the zero-field-cooled/field cooled (ZFC/FC) curves confirm the spin reversal observed in bulk samples, the remarkable effects seen on hysteresis loops for bulk samples were not present in single crystals, probably due to oxygenation conditions. On the other hand, a very large anisotropy was observed between two perpendicular orientations of the single crystal.