Magnetic and anisotropic magnetocaloric effects of HoCoSi fast quenching ribbons

Abstract

The performance of magnetocaloric effect materials is one of the key factors restricting the development of magnetic refrigeration technology. Materials with anisotropic magnetocaloric effect can be used in the rotary magnetic refrigeration technology, which is beneficial to the simplification of refrigeration devices. In this work, the magnetic properties, magnetocaloric effects, and magnetic anisotropies of rapidly quenched HoCoSi compounds are investigated. At low temperatures below <i>T</i><sub>t</sub> = 5.7 K, the HoCoSi ferromagnetism and helical magnetism coexist. With the increase of temperature, the HoCoSi undergoes a second-order phase transition from ferromagnetic (FM) to paramagnetic (PM) phase at <i>T</i><sub>C</sub> = 13.7 K. Both XRD and SEM show that the HoCoSi has a preferred orientation. In order to obtain a large magnetocaloric effect and to determine the effect of preferred orientation on magnetism and magnetocaloric effect, the isothermal magnetization curves of the 10 m/s–HoCoSi fast quenched belt in the directions of <i>H</i> parallel and perpendicular to texture around the Curie temperature are analyzed. The corresponding magnetic entropy change (–Δ<i>S</i><sub>M</sub>) and magnetic refrigeration capacity (RC) are calculated. Under the magnetic field changing from 0 to 5 T, the value of –Δ<i>S</i><sub>M</sub> is 22 J/(kg·K) in the direction of <i>H</i> parallel to the texture and 12 J/(kg·K) in the direction of <i>H</i> perpendicular to texture , and their corresponding values of RC(RCP)are 360 (393.8) J·kg<sup>–1</sup> and 160 (254.4) J/kg. The value of –Δ<i>S</i><sub>M</sub> reaches 12.5 J/(kg·K)even at <i>μ</i><sub>0</sub><i>H</i> = 0–2 T in the direction of H parallel to the texture. It is obvious that the 10-m/s-HoCoSi fast quenching belt shows a large low-field magnetocaloric effect and obvious magnetic anisotropy, which is expected to be used to realize the magnetic refrigeration technology of rotating samples.