Temperature dependence of magnetic anisotropy constant in iron chalcogenide Fe(3)Se(4): Excellent agreement with theories.

Magnetic hysteresis loops were measured for ferrimagnetic iron chalcogenide [Formula: see text] nanoparticles in the whole temperature range below the Curie temperature [Formula: see text] (315 K). The coercivity of the material is huge, reaching about 40 kOe at 10 K. The magnetic anisotropy constant K was determined from the magnetic hysteresis loop using the law of approach to saturation. The deduced anisotropy constant at 10 K is [Formula: see text], which is over one order of magnitude larger than that of [Formula: see text]. We also demonstrated that the experimental magnetic hysteresis loop is in good agreement with the theoretical curve calculated by Stoner and Wohlfarth for a noninteracting randomly oriented uniaxial single-domain particle system. Moreover, we show that K is proportional to the cube of the saturation magnetization [Formula: see text], which confirms earlier theoretical models for uniaxial magnets.