Thermomagnetic properties of fine-grain polycrystalline GdIG

Thermomagnetic properties of fine-grain polycrystalline GdIG were investigated in two ways. First the hysteresis loop was observed on bulk material as well as on thin wafers over the temperature range 0-70°C. The remanent flux density Br, the squareness ratio , and the coercive force Hcwere found to be quite temperature dependent. The effects of stresses and grain size on the Hcvalue were measured. These properties were explained in terms of domain-wall dynamics. A second set of experiments was the study of dynamic thermomagnetic laser recording on GdIG as a storage medium. The writing and reading parameters were examined. A bit diameter of 15 μm was currently written with 100-mW 1-μs pulses together with a 250-Oe bias field. Readout at rates of up to 10⁶bit/s was obtained for densities larger than 10⁶bit/in². The stability of written bits was studied versus time or temperature changes and correlated with the magnetic properties.