Abstract
MnCoGe1-xVx (x = 0.005, 0.01, 0.015, 0.02, 0.03, and 0.04) compounds were synthesized and investigated in view of the effect of transition metals on main-group-element sites to the magnetostructural transition. A small amount of V doping results in a decrease of the martensitic transformation temperature, while a further increase of V disturbs the Co-Ge bonds hence destabilizing the MM’X phase. Therefore, the transformation temperature returns to high temperature, and the expected Curie temperature window becomes incomplete. Accordingly, a large magnetic entropy change of about 10 J/kg·K and a refrigerant capacity of about 129.5 J/kg is obtained in the series.
Highlights
Most studies on magnetic refrigeration are focused on materials undergoing a first-order magnetic phase transition due to their large magnetocaloric effect.1–7 Amongst many kinds of such materials, the well-known MM’X family is interesting for its unique ‘Curie temperature window’ (CTW) phenomenon.1–4 These compounds show a martensitic transformation from the hightemperature Ni2In-type hexagonal structure to the low-temperature TiNiSi-type orthorhombic structure.5–10 to the best of our knowledge, the structural transition (TM) of the MM’X systems known so far occurs at higher temperatures than the Curie temperature of martensite (TCM), implying that they are not coupled together
Studies on Mnvacancy in MnCoGe systems show that Co atoms could fill in Mn vacancies, resulting in the appearance of Co vacancy and the TM can be adjusted to lower temperatures
As the further increase of V, the hexagonal phase becomes dominant gradually, indicating that the martensitic transformation temperatures TM has been decreased to near room temperature
Summary
Most studies on magnetic refrigeration are focused on materials undergoing a first-order magnetic phase transition due to their large magnetocaloric effect. Amongst many kinds of such materials, the well-known MM’X family is interesting for its unique ‘Curie temperature window’ (CTW) phenomenon. These compounds show a martensitic transformation from the hightemperature Ni2In-type hexagonal structure to the low-temperature TiNiSi-type orthorhombic structure. to the best of our knowledge, the structural transition (TM) of the MM’X systems known so far occurs at higher temperatures than the Curie temperature of martensite (TCM), implying that they are not coupled together. Amongst many kinds of such materials, the well-known MM’X family is interesting for its unique ‘Curie temperature window’ (CTW) phenomenon.. Amongst many kinds of such materials, the well-known MM’X family is interesting for its unique ‘Curie temperature window’ (CTW) phenomenon.1–4 These compounds show a martensitic transformation from the hightemperature Ni2In-type hexagonal structure to the low-temperature TiNiSi-type orthorhombic structure.. Studies on Mnvacancy in MnCoGe systems show that Co atoms could fill in Mn vacancies, resulting in the appearance of Co vacancy and the TM can be adjusted to lower temperatures.. Studies on Mnvacancy in MnCoGe systems show that Co atoms could fill in Mn vacancies, resulting in the appearance of Co vacancy and the TM can be adjusted to lower temperatures.1 Apart from this method, introducing interstitial atoms or physical hydrostatic pressure in MnCoGe system can effectively tune the structural transition temperature Studies on Mnvacancy in MnCoGe systems show that Co atoms could fill in Mn vacancies, resulting in the appearance of Co vacancy and the TM can be adjusted to lower temperatures. Apart from this method, introducing interstitial atoms or physical hydrostatic pressure in MnCoGe system can effectively tune the structural transition temperature
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