Abstract 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 H K , the reduced remanence M r / M s , and the coercive field H C 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.