X-ray powder spectroscopy to determine easy axis in colloidal magnetic particles

Non-interacting suspended colloidal single-domain magnetic particles can be expected to acquire a preferred orientation in a magnetic field. Their direction is determined by the easy magnetization axes of the particle and the applied field to a degree determined by the Langevin equation governing paramagnetic phenomena. The magnitudes of resulting changes in powder line intensities have been calculated and found to be of the order of 5 to 25% for ferrite particles near the critical size (where anisotropy energy ≥kT), the larger for larger particles. The pattern of line intensity changes allows one to distinguish between (1,0,0) and (1,1,1) easy axes. (orig.)