Magnetic Properties and Phase Diagram of Co_<i>x</i>Mn_1-<i>x</i>TiO₃with Exchange Frustration

Abstract

Low-field DC magnetization measurements have been made on a random mixture Co x Mn 1- x TiO 3 with competing exchange interactions and competing anisotropies, and the magnetic phase diagram in the concentration ( x )-temperature ( T ) plane has been determined from these results. Typical behavior characterizing a paramagnetic to spin glass transition is observed in an intermediate range of concentration. In the samples of the Co-rich and Mn-rich region, antiferromagnetic orderings take place. The magnetizations perpendicular to the spin axes of the respective antiferromagnetic orderings behave just as paramagnets even below the Néel temperature. At low temperatures, the Co-rich and Mn-rich samples with certain x reenter from the antiferromagnetic phase to the spin glass phase. In spite of the strong planar anisotropy of Co 2+ , the XY -like spin glass behavior has not been found, and the spin glass and reentrant transition in S // and S ⊥ occur simultaneously, reasons for which are discussed.