The second-order magnetic phase transition and magnetocaloric effect in all-d-metal NiCoMnTi-based Heusler alloys
F. Zhang (TU Delft - RST/Fundamental Aspects of Materials and Energy)
Kevin Westra (Student TU Delft)
Q. Shen (TU Delft - RST/Fundamental Aspects of Materials and Energy)
I. Batashev (TU Delft - RST/Fundamental Aspects of Materials and Energy)
A. Kiecana (TU Delft - RST/Fundamental Aspects of Materials and Energy)
N.H. van Dijk (TU Delft - RST/Fundamental Aspects of Materials and Energy)
E.H. Brück (TU Delft - RST/Fundamental Aspects of Materials and Energy)
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Abstract
The novel all-d-metal Ni(Co)MnTi based magnetic Heusler alloys provide an adjustable giant magnetocaloric effect and good mechanical properties. We report that the second-order magnetic phase transition can be tailored in this all-d-metal NiCoMnTi based Heusler system by optimizing the Mn/Ti ratio, resulting in a reversible ferromagnetic-to-paramagnetic magnetic transition. A candidate material Ni33Co17Mn30Ti20 with a magnetic entropy change ∆Sm of 2.3 Jkg−1K−1 for a magnetic field change of 0–5 T, has been identified. The TC and saturation magnetization MS can be controlled by adjusting the Ni/Co concentration and doping non-magnetic Cu atoms. The compositional maps of TC and MS have been established. Density functional theory (DFT) calculations reveal a direct correlation between the magnetic moments and the Co content. By combining XRD, SQUID, SEM and DFT calculations, the (micro)structural and magnetocaloric properties have been investigated systematically. This study provides a detailed insight in the magnetic phase transition for this all-d-metal Ni(Co)MnTi-based Heusler alloy system.
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