Nonhysteretic metamagnetic phase transition in Ho₂In_1-xAl_x (0 ≤ x ≤ 0.4) by hetero-structural alloying

By hetero-structural alloying ferromagnetic hexagonal Ho₂In with antiferromagnetic orthorhombic Ho₂Al, the magnetic and structural changes have been observed in Ho₂In_1-xAl_x (0 ≤ x ≤ 0.4) alloys. At the critical composition x = 0.1, the highest maxima of magnetic entropy change of 16.3 Jkg^-1K⁻¹ and the adiabatic temperature change of 6.5 K have been obtained via an unconventional hysteresis-free metamagnetic phase transitionm, which is higher than 9 Jkg^-1K⁻¹ and 5.4 K in Ho₂In benchmark alloy undergoing second-order phase transition. Such increment is associated with the intensified magnetoelastic coupling. The deeper origin is proposed to be from the delocalized 5d electrons of rare-earth atoms by external field since the magnetoresistence is also maximized at the critical composition. The hetero-structural alloying strategy is demonstrated to be effective to intensify the MCE effect without causing the undesirable hysteresis.