Physical properties of Mn based full heusler alloys

Abstract

The investigation of the physical properties of a few Mn-based full Heusler alloys newlineis documented in this thesis work and the key results are summarized in Table newline7.1. Out of the studied compositions, Mn1.5Fe1.5Al and Mn50Fe25+xAl25and#8722;x Heusler newlinealloys possess a and#946;-Mn cubic crystal structure where the inherent geometrical frustration newlineleads to a low-temperature spin-glass-like state along with an antiferromagnetic newlineordering. In the bulk Al2MnFe Heusler alloy, a B2 cubic disordered newlinecrystal structure with a ferromagnetic ground state is observed. The Al2MnFe newlinealloy belongs to the 3D-Heisenberg universality class having isotropic short-range newlinemagnetic interactions and shows tremendous potential for magnetocaloric applications. newlineThe experimental investigation on Mn2CuGe confirms its ferrimagnetic newlineground state that is consistent with the theoretical predictions. Interestingly, all newlinethe studied alloys show a low-temperature SG behavior irrespective of their composition, newlinecrystal structures, or magnetic ground states (FM, AFM or FiM). newlineAll the polycrystalline alloys studied in this thesis work are prepared using a mini newlinearc-melting (MAM-I) facility in the Department of Physics at Central University newlineof Rajasthan. newlineA detailed study on the structural, and static and dynamic magnetic properties newlineof the arc-melted polycrystalline Mn1.5Fe1.5Al Heusler type alloy suggests that newlinethe alloy crystallizes in a and#946;-Mn type cubic crystal structure. The analysis of the newlinetemperature-dependent DC magnetization measurements reveals the existence of newlinedominant antiferromagnetic interactions and a high degree of frustration (frustration newlineparameter fp and#8764; 18.7). Moreover, a peak in the ZFC magnetization along with newlinea bifurcation of the ZFC and FC curves, shifting of the ZFC peak towards lower newlinetemperature with increasing magnetic field, the exponential decay of coercivity newlineand remanence with temperature, and unidirectional exchange bias effect suggest newlinea spin-glass behavior of the sample. This is confirmed through extensive AC susceptibility newlineanalysis.