First-order non-hysteretic phase transition: a pathway to enhanced magnetocaloric and giant magnetoresistance effects in a Gd-Al alloy.

Fascinating physical phenomena often occur near the phase transition points in materials. This study provides a comprehensive investigation into the structural and magnetic properties of a Gd-Al alloy using both experimental and theoretical methods. The results indicate that the Gd-Al alloy exhibits a distinct antiferromagnetic phase transition under a low magnetic field. Theoretical calculations show a non-collinear alignment of magnetic moments on a crystal plane parallel to (001). A non-hysteretic metamagnetic transition, which suggests a magnetoelastic transition with discontinuous volume changes, is observed when the external magnetic field increases. The alloy demonstrates a significant magnetic entropy change of 16.5 J kg K at a field variation of 7 T. Additionally, it displays a giant magnetoresistance effect at low temperatures under the same field conditions. Electronic structure calculations reveal a high density of states (DOS) value near the Fermi level, mainly due to the Gd 5d electrons. The hybridization of Gd 5d and Al 2p orbitals, along with the observed 5d-4f hybridization near the , plays a crucial role in the electronic structure. This systematic analysis highlights the importance of an elevated DOS at the Fermi level in enabling the metamagnetic transition, which promotes the application of the Gd-Al alloy in energy-related fields.