HoCoSi快淬带的磁性和各向异性磁热效应

Magnetic and anisotropic magnetocaloric effects of HoCoSi fast quenching ribbons

磁制冷技术的发展取决于磁热效应材料的研究进展.其中,具有各向异性磁热效应的材料可以用于旋转磁制冷技术,有利于制冷装置的大幅度简化.本文研究了快淬带Ho Co Si化合物的磁性、磁热效应及磁各向异性.在Tt=5.7 K以下的低温,Ho Co Si快淬带铁磁和螺旋磁性共存,随着温度的升高,在TC=13.7 K处发生了铁磁(FM)到顺磁(PM)的二级相变.XRD和SEM都显示出Ho Co Si具有择优取向.为了获得大的磁热效应并确定择优取向对磁性和磁热效应的影响,对10 m/s下Ho Co Si快淬带在磁场平行和垂直织构方向时居里温度附近的等温磁化曲线进行分析,并计算了对应的磁熵变和磁制冷能力.在外磁场μ0H=0—5 T的磁场变化时,磁场平行和垂直织构方向的最大磁熵变值–ΔSM分别为22 J/(kg·K)和12 J/(kg·K);制冷能力RC(RCP)分别为360(393.8)J/kg和160(254.4)J/kg,表明10 m/s的Ho Co Si快淬带具有大的磁热效应和明显的磁各向异性,有望实现旋转样品磁制冷技术.

The performance of magneto caloric 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 Tt=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 T_(C)=13.7 K.Both XRD and SEM show that the HoCoSi has a preferred orientation.In order to obtain a large magneto caloric effect and to determine the effect of preferred orientation on magnetism and magneto caloric effect,the isothermal magnetization curves of the 10 m/s-HoCoSi fast quenched belt in the directions of H parallel and perpendicular to texture around the Curie temperature are analyzed.The corresponding magnetic entropy change(-ΔS_(M)) and magnetic refrigeration capacity(RC) are calculated.Under the magnetic field changing from 0 to 5 T,the value of-ΔS_(M) is 22 J/(kg·K) in the direction of H parallel to the texture and 12 J/(kg·K) in the direction of H perpendicular to texture,and their corresponding values of RC(RCP)are 360(393.8) J·kg^(-1) and 160(254.4) J/kg.The value of-ΔS_(M) reaches 12.5 J/(kg·K)even at μ_(0) H=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.