Ho2Fe11Al6金属间化合物的低温零热膨胀及其机制

稀土-过渡金属元素(Rare earth-transition metal, R-TM)构成的金属间化合物具有良好的永磁、磁热和磁弹性能。近年来,新型负热膨胀化合物的探索及其机制研究作为一个新兴的研究领域被广泛关注。通过高分辨同步辐射X射线和中子衍射对Ho2Fe11Al6化合物的反常热膨胀行为进行了研究。从原子磁矩随温度变化的角度定量揭示了磁致体积效应(Magneto-volume effects, MVEs)的成因:随着温度升高,铁原子的磁矩持续降低,使得磁致体积效应逐渐削弱;低温下,与原子间非简谐振动导致的体积正热膨胀相抵消,从而晶格出现持续的零热膨胀行为。在温度高于居里温度时,磁有序消失,晶格表现正常的正热膨胀。结合其本征金属性, Ho2Fe11Al6的低温零热膨胀性在未来高精度度量和定位仪器具有潜在的应用价值。

Zero Thermal Expansion and Its Mechanism of Ho2Fe11Al6 Intermetallic Compounds at Low Temperature

Rare earth-transition metal(R-TM) intermetallic compounds exhibit good performance on permanent magnetism, magneto-caloric and magneto-volume effects(MVEs). Recently, the exploration of new negative thermal expansion(NTE) materials and mechanism has been widely considered as a novel research field. Here, abnormal thermal expansion behavior of Ho2Fe11Al6 compounds was comprehensively investigated by synchrotron X-ray and Neutron powder diffraction. It revealed that the magneto-volume effects were dominated by the atomic magnetic moments: the decrease of Fe-sublattice moments weakened the MVEs upon heating, which fully compensated for the positive thermal expansion induced by phonon vibration at low temperature, yielding zero thermal expansion(ZTE). Furthermore, the abnormal thermal expansion vanished due to the degraded magnetic ordering above Curie temperature. The ZTE behavior of Ho2Fe11Al6 intermetallic compound might have potential industrial merits in the future.