Effect of Carbon Doping on the Structure and Magnetic Phase Transition in (Mn,Fe2(P,Si))

Abstract

Given the potential applications of (Mn,Fe 2 (P,Si))-based materials for roomtemperature magnetic refrigeration, several research groups have carried out fundamental studies aimed at understanding the role of the magneto-elastic coupling in the first-order magnetic transition and further optimizing this system. Inspired by the beneficial effect of the addition of boron on the magnetocaloric effect of (Mn,Fe 2 (P,Si))-based materials, we have investigated the effect of carbon (C) addition on the structural properties and the magnetic phase transition of Mn 1:25 Fe 0:70 P 0:50 Si 0:50 C z and Mn 1:25 Fe 0:70 P 0:55 Si 0:45 C z compounds by x-ray diffraction, neutron diffraction and magnetic measurements in order to find an additional control parameter to further optimize the performance of these materials. All samples crystallize in the hexagonal Fe 2 Ptype structure (space group P-62m), suggesting that C doping does not affect the phase formation. It is found that the Curie temperature increases, while the thermal hysteresis and the isothermal magnetic entropy change decrease by adding carbon. Room-temperature neutron diffraction experiments on Mn 1:25 Fe 0:70 P 0:55 Si 0:45 C z compounds reveal that the added C substitutes P/Si on the 2c site and/or occupies the 6k interstitial site of the hexagonal Fe 2 Ptype structure.

Iron and manganese based magnetocaloric materials for near room temperature thermal management

“…The influence of carbon addition on the structure, magnetic phase transition and MCE of Mn1.25Fe0.70P0.50Si0.50Cz and Mn1.25Fe0.70P0.55Si0.45Cz compounds synthesized by high-energy ball milling and a solid-state reaction was recently examined [198]. The C doping was found to be helpful for tuning the TC of the alloys and to reduce thermal hysteresis.…”

Effect of Co and Ni Doping on the Structure, Magnetic and Magnetocaloric Properties of Fe-Rich (Mn,Fe)2(P,Si) Compounds

“…However, controlling the thermal hysteresis originating from the first-order magnetic transition (FOMT) is a prerequisite for practical applications. The character of the transition and the magnitude of hysteresis can be tuned by utilizing appropriate doping, e. g., V, B, C, N, and changes in the heat treatment [11][12][13][14][15][16]. Various studies show that Co doping of (Mn,Fe) 2 (P,Si) compounds can effectively reduce the thermal hysteresis and the transition temperature [5,17,18].…”

Magnetic Phase Diagram of the MnxFe2−xP1−ySiy System

“…The Mn-Fe-P-Si composition of these materials may have a distinct effect on the structural and magnetic properties. In addition, the introduction of small atoms like boron, carbon and nitrogen can also be used to tailor the magnetoelastic transition for the (Mn,Fe) 2 (P, Si) compounds while preserving a giant MCE [ 29 , 30 , 31 , 32 ].…”