Magnetic and structural instabilities in mictomagnetic Cu50Mn45Al5 against the formation of ferromagnetic precipitates

A new property of Heusler alloys known as shell-ferromagnetism is observed predominantly in NiMn-based Heusler alloys with X as Ga, Al, In and Sn. An antiferromagnetic-matrix/shell-ferromagnetic precipitate dual-phase generates from an anti-ferromagnetic initial structure with temper-annealing in an external magnetic field. The present study focuses on the magnetic and structural instabilities in CuMn-based Cu50Mn45Al5 Heusler alloy when temper-annealed under a magnetic field, as in NiMn-based Heusler alloys. The ternary Cu50Mn45Al5 Heusler alloy exhibits a cubic mictomagnetic structure in its initial state. Structural decomposition occurs during temper-annealing under a magnetic field from the initial state to a triple-phase composite alloy. The decomposed phases are identified to be cubic L2(1) Cu2MnAl, cubic L1(0)Cu(50)Mn(50) and A13 beta-Mn. As observed in shell-ferromagnetism, the ferromagnetic Cu-2 MnAl precipitates form in a mictomagnetic CuMn matrix with an additional beta-Mn component.