Nonhysteretic metamagnetic phase transition in Ho2In1-xAlx (0 ≤ x ≤ 0.4) by hetero-structural alloying

•The hexagonal structure observed for x ≤ 0.1 while orthorhombic one for ≥ 0.2.•The first-order-like phase transition is observed near critical composition of x = 0.1.•The largest ΔSmax of 16.3 Jkg-1K−1 and ΔTad of 6.5 K is realized by a nonhysteretic metamagnetic phase transition.•Improved performance is contributed from the enhanced magnetoelastic coupling.•It is explained by the delocalized Ho 5d electrons and further proved by the increased ΔR/R in Ho2In0.9Al0.1 alloy. By hetero-structural alloying ferromagnetic hexagonal Ho2In with antiferromagnetic orthorhombic Ho2Al, the magnetic and structural changes have been observed in Ho2In1-xAlx (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.