Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, Florida 32306, United States.
J Am Chem Soc. 2013 Jun 26;135(25):9553-7. doi: 10.1021/ja404107p. Epub 2013 Jun 18.
AlFe2B2 was prepared by two alternative synthetic routes, arc melting and synthesis from Ga flux. In the layered crystal structure, infinite chains of B atoms are connected by Fe atoms into two-dimensional [Fe2B2] slabs that alternate with layers of Al atoms. As expected from the theoretical analysis of electronic band structure, the compound exhibits itinerant ferromagnetism, with the ordering temperature of 307 K. The measurement of magnetocaloric effect (MCE) as a function of applied magnetic field reveals isothermal entropy changes of 4.1 J kg(-1) K(-1) at 2 T and 7.7 J kg(-1) K(-1) at 5 T. These are the largest values observed near room temperature for any metal boride and for any magnetic material of the vast 122 family of layered structures. Importantly, AlFe2B2 represents a rare case of a lightweight material prepared from earth-abundant, benign reactants which exhibits a substantial MCE while not containing any rare-earth elements.
AlFe2B2 是通过两种替代的合成路线制备的，即电弧熔炼和 Ga 通量合成。在层状晶体结构中，无限的 B 原子链通过 Fe 原子连接成二维[Fe2B2]薄片，这些薄片与 Al 原子层交替排列。正如电子能带结构理论分析所预期的那样，该化合物表现出巡游铁磁性，有序温度为 307 K。对磁热效应（MCE）随外加磁场的测量表明，在 2 T 时的等温熵变化为 4.1 J kg-1 K-1，在 5 T 时为 7.7 J kg-1 K-1。这些是在室温附近观察到的任何金属硼化物和 122 族层状结构中任何磁性材料的最大值。重要的是，AlFe2B2 代表了一种由丰富、良性反应物制备的轻量级材料的罕见实例，它在不包含任何稀土元素的情况下表现出显著的磁热效应。
