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We report variations in the coercivity of Co[Fe.sub.2][O.sub.4] nanoparticles as a function of particle size, temperature and light intensity. For 30 nm particles, this change in was 2300 Oe at 10K, 120 Oe at 170K, for a light intensity of under 2 milliwatts. The remanent magnetization was nearly unchanged by illumination. A simple model of optical absorption followed by electron transfer between [Co.sup.2+] and [Fe.sup.3+] ions is proposed. Index Terms--Cobalt ferrite, coercivity, photomagnetic effect, remanent magnetization.

Pulsed-current controlled wall motion in 20 [micro]m wide x 200 [micro]m long x 160 nm thick patterned Permalloy strips was studied using magnetic force microscopy. By sequential imaging, the displacement of Bloch walls as far as 200 [micro]m along the strip was observed. The direction of motion was in the same direction as the carrier velocity, which reversed with current polarity. The displacement per pulse was dependent upon the sample thickness and current density, which suggests that the mechanism is a combination of s-d exchange and hydromagnetic domain drag forces. Index Terms--Permalloy, current pulse, domains, Bloch wall, s-d exchange, domain drag, MFM, magnetization switching.