Evidence for canonical spin glass behaviour in polycrystalline Mn1.5Fe1.5Al Heusler alloy.

• Mn 1.5 Fe 1.5 Al alloy with a β-Mn structure exhibits canonical spin-glass behaviour. • Large frustration parameters indicting high degree of frustration is measured. • Hierarchical model of the spin-glass magnetic relaxation is observed. • Unidirectional exchange bias effect and memory effect are also observed. Magnetic properties of magnetically frustrated polycrystalline Mn 1.5 Fe 1.5 Al Heusler type alloy with a β-Mn structure were systematically studied using dc magnetization, ac susceptibility, magnetic relaxation and magnetic memory effect measurements to understand its magnetic ground state. The Mn 1.5 Fe 1.5 Al alloy system exhibits a sharp peak at low temperature around 34.5 K with strong antiferromagnetic correlations (θ CW ∼ −639 K) and a high degree of frustration (f p ∼ 18.7) which suggest the presence of competing magnetic interactions. Despite of strong antiferromagnetic correlations, this peak has spin-glass character as confirmed by the observations of bifurcation of the zero-field-cooled and field-cooled magnetization curves below the irreversibility temperature, field dependent shift of the irreversibility temperature, unidirectional exchange bias effect on the field-cooled M-H hysteresis loop, exponential decay of the temperature variation of remanence and coercivity, frequency dependent shift of the spin glass freezing temperature (T f) as per the dynamic scaling laws given by the critical slowing down model and Vogel-Fulcher law, magnetic relaxation and magnetic memory effect below T f. The observation of a clear asymmetric response with respect to the temperature cycling in the magnetic relaxation measurements validates the hierarchical model of the spin-glass magnetic relaxation in Mn 1.5 Fe 1.5 Al alloy. Since the behaviour exhibited by the Mn 1.5 Fe 1.5 Al alloy has perfect similarity with the well-known atomic spin glasses like CuMn, AuFe, therefore, it may be considered as canonical spin-glass system. [ABSTRACT FROM AUTHOR]