Magnetic behavior of a reentrant Ising spin glass.

Abstract

The ac susceptibility of the reentrant Ising spin glass ${\mathrm{Fe}}_{0.62}$${\mathrm{Mn}}_{0.38}$${\mathrm{TiO}}_{3}$ has been investigated in a superconducting-quantum-interference-device magnetometer. The data show a transition from a paramagnetic to an antiferromagnetic state at ${\mathit{T}}_{\mathit{N}}$=32.8 K. At lower temperatures, the in-phase component of the susceptibility, \ensuremath{\chi}'(\ensuremath{\omega}), becomes frequency dependent and, simultaneously, a finite out-of-phase component of the susceptibility, \ensuremath{\chi}''(\ensuremath{\omega}), appears. This behavior is interpreted to arise from a transition to a mixed spin-glass and antiferromagnetic state at ${\mathit{T}}_{\mathit{g}}$=25.8 K. A dynamic scaling analysis of \ensuremath{\chi}''(\ensuremath{\omega}) yields critical exponents quite different from those found for the pure Ising spin glass ${\mathrm{Fe}}_{0.5}$${\mathrm{Mn}}_{0.5}$${\mathrm{TiO}}_{3}$. However, some apparent deviations from optimal scaling behavior are observed. Magnetic relaxation experiments on this reentrant spin glass reveal the existence of an aging phenomenon similar to that observed in ordinary spin glasses. It is also found that the behavior of the magnetic relaxation can be interpreted within the context of spin-glass domain theories.