Magnetocaloric properties and critical behavior of Co2Cr1−xMnxAl Heusler alloys

We study the magnetocaloric effect and critical behavior of Co 2 Cr 1 − x Mn x Al ( x = 0.25, 0.5, 0.75) Heusler alloys across the ferromagnetic (FM) transition temperature ( T C). The Rietveld refinement of x-ray diffraction patterns exhibit a single phase cubic structure for all the samples. The temperature dependent magnetic susceptibility χ ( T ) data show a systematic enhancement in the Curie temperature and effective magnetic moment with the Mn concentration, which is consistent with the Slater–Pauling behavior. The M ( H ) isotherms also exhibit the FM ordering, and the analysis of χ ( T ) data indicates the nature of the phase transition to be a second order, which is further supported by scaling of the entropy curves and the Arrott plot. Interestingly, the Mn substitution causes an increase in the magnetic entropy change and, hence, a large relative cooling power for possible applications in multistage magnetic refrigerators. In order to understand the nature of the magnetic phase transition, we examine the critical exponents β, γ, δ for the x = 0.75 sample by the modified Arrott plot and the critical isotherm analysis, which is further confirmed by the Kouvel-Fisher method and Widom scaling relation, respectively. The estimated values of β = 0.507, γ = 1.056, δ = 3.084 are found to be close to the mean field theoretical values. The renormalized isotherms (m vs h) corresponding to these exponent values collapse into two branches, above and below T C that validates our analysis. Our results suggest the existence of long-range FM interactions, which decays slower than power law as J ( r ) ∼ r − 4.5 for a three-dimensional mean-field theory.We study the magnetocaloric effect and critical behavior of Co 2 Cr 1 − x Mn x Al ( x = 0.25, 0.5, 0.75) Heusler alloys across the ferromagnetic (FM) transition temperature ( T C). The Rietveld refinement of x-ray diffraction patterns exhibit a single phase cubic structure for all the samples. The temperature dependent magnetic susceptibility χ ( T ) data show a systematic enhancement in the Curie temperature and effective magnetic moment with the Mn concentration, which is consistent with the Slater–Pauling behavior. The M ( H ) isotherms also exhibit the FM ordering, and the analysis of χ ( T ) data indicates the nature of the phase transition to be a second order, which is further supported by scaling of the entropy curves and the Arrott plot. Interestingly, the Mn substitution causes an increase in the magnetic entropy change and, hence, a large relative cooling power for possible applications in multistage magnetic refrigerators. In order to understand the nature of the magnetic p...