Magnetic properties of barium ferrite nanoparticles: Quantitative test of the Stoner-Wohlfarth theory for uniaxial single-domain magnetic particles

We have successfully synthesized single-domain barium ferrite particles with uniaxial anisotropy. We have coated them with amorphous silica to reduce interparticle interactions so that the assembly of these particles behaves like a noninteracting randomly oriented uniaxial single-domain particle system, a prototype for the Stoner-Wohlfarth model. From the magnetic hysteresis loops of the particle system in a wide temperature range (10-700 K), we simultaneously determine the magnetic anisotropic field HK, the reduced remanence Mr/Ms, and the coercive field HC in the whole temperature range below the Curie temperature. These complete sets of data allow us to quantitatively test the Stoner-Wohlfarth theory and the agreement between experiment and theory is good.