Size effects on the magnetic properties of fine Fe‐Cr particles (abstract)

The magnetic and structural properties of Fe100−xCrx ultrafine particles with x=5–20 have been studied as a function of particle size. Particles with sizes in the range of 100–450 A were prepared by gas evaporation under Ar atmosphere. The particles had a high coercivity with the smaller particles showing a stronger temperature dependence of coercivity than the larger particles. In the smaller x=5 particles the coercivity was about 2500 Oe at 10 K and 100 Oe at room temperature. The temperature coefficient of coercivity of Fe‐Cr fine particles was smaller than that of Fe particles.1 Mossbauer spectroscopy was used in the temperature range of 4.2–300 K to better understand the magnetic hysteresis behavior of the particles. The spectra showed the presence of Fe‐Cr, α‐Fe, and Fe‐oxide components in the larger particles, and Fe‐Cr and Fe oxide in the smaller particles. The coercivity at low temperature is increased with decreasing particle size and this is attributed to the higher percentage of Fe oxide in th...