Effect of Random Fields on the Phase Diagram of the Diluted Antiferromagnet Mn0.80Mg0.20TiO3in the Field-Temperature Plane

Abstract

The diluted antiferromagnet Mn 0.80 Mg 0.20 TiO 3 has been studied by measuring magnetization processes and temperature variations of magnetization, and the magnetic phase diagram in the field-temperature ( H - T ) plane has been determined. It is demonstrated that the existence of random fields strongly affects the phase transitions. The most noteworthy result is that the H - T phase diagram consists of four phases instead of the generally known three phases: a paramagnetic, an antiferromagnetic and a spin-flop phase. We propose that the fourth phase corresponds to the region in the H - T phase diagram of Mn 0.75 Zn 0.25 F 2 where the behavior of the spin system is suggested to be anomalous by Cowley et al . (Z. Phys. B 75 (1989) 303).