Magnetic proximity effect and shell-ferromagnetism in metastable Ni50Mn45Ga5

The present study on magnetic and structural properties of Ni50Mn45Ga5 confirms that structural metastability is an inherent property of Ni50Mn50– x X x Heusler alloys with X as In, Ga, and Sn. The ternary alloy transforms during temper-annealing into a dual-phase composite alloy. The two phases are identified to be cubic L21, Ni50Mn25Ga25, and tetragonal L10 Ni50Mn50. Depending on the annealing temperature, the magnetic-proximity effect giving rise to shell-ferromagnetism has been observed when annealing is carried out under an external magnetic field. The upper and lower remanence values M R + and M R − have the same sign even at high temperatures. Such alloys can be promising candidates for heat- and magnetic-field-resistant magnetic recording media.