Magnetic properties of Co_50-xNi_xMn ₂₅Al₂₅ alloys with B2 structure

Magnetic properties of the B2 phase in Co_50-xNi _xMn₂₅Al₂₅ alloys were investigated. Spontaneous magnetization M_s measured at 4.2 K increases linearly with increasing x in the region of x ≤ 30 in accordance with following the generalized Slater-Pauling (GSP) line. However, M_s abruptly decreases with increasing x and deviates from the GSP line in the Ni-rich region of x > 30, suggesting a drastic change in the density of states at the Fermi energy. The Curie temperature T_C decreases monotonically with increasing x and significantly decreases in the region of x > 30. Antiferromagnetic evidence is clearly observed at x > 45, and the Néel temperature T_N increases with increasing x, in reaching the value of the B2 phase in Ni₂MnAl.