Cluster spin-glass behaviour and memory effect in Cr$_{0.5}$Fe$_{0.5}$Ga

Abstract

We report the structural, static, and dynamic properties of Cr0.5Fe0.5Ga by means of powder x-ray diffraction, DC magnetization, heat capacity, AC susceptibility, magnetic relaxation, and magnetic memory effect measurements. DC magnetization and AC susceptibility studies reveal a spin-glass transition at around T f 22 K. An intermediate value of the relative shift in freezing temperature δT f 0.017, obtained from the AC susceptibility data reflects the formation of cluster spin-glass states. The frequency dependence of T f is also analyzed within the framework of dynamic scaling laws such as power law and Vogel-Fulcher law. The analysis using power law yields a characteristic time constant for a single spin flip τ * 1.1 × 10 −10 s and critical exponent zν = 4.2 ± 0.2. On the other hand, the Vogel-Fulcher law yields the characteristic time constant for a single spin flip τ06.6 × 10 −9 s, Vogel-Fulcher temperature T0 = 21.1 ± 0.1 K, and an activation energy Ea/kB 16 K. The value of τ * and τ0 along with a non-zero value of T0 provide further evidence for the cluster spin-glass behaviour. The magnetic field dependent T f follows the de Almeida-Thouless (AT) line with a non-mean-field type instability, reflecting either a different universality class or strong anisotropy in the spin system. A detailed non-equilibrium dynamics study via relaxation and memory effect experiments demonstrates the evolution of the system through a number of intermediate metastable states and striking memory effects. All the above observations render a cluster spin-glass behaviour in Cr0.5Fe0.5Ga which is triggered by magnetic frustration due to competing antiferromagnetic and ferromagnetic interactions and magnetic site disorder. Moreover, the asymmetric response of magnetic relaxation with respect to the change in temperature, below the freezing temperature can be explained by the hierarchical model.

A spin glass state in Ba3TiRu2O9

“…When the field is increased to 2.5 kOe, Tf is shifted down to 3.8 K. At the field of 1 T, it is moved to 2.5 K. Above 2 T, the freezing temperature is further suppressed below 2 K and is not detected in our measurements. This is similar to the cluster spin glass behavior seen in Cr0.5Fe0.5Ga (21) . The resistivity of Ba3TiRu2O9 as a function of reciprocal temperature is plotted in Figure 3b.…”