Abstract: Comparison of magnetic and crystalline profiles in He+-implanted Gd,Tm,Ga:YIG

Abstract

Profiles of magnetic and crystalline properties in He+-implanted <111>-oriented Gd,Tm,Ga:YIG were obtained using ferromagnetic resonance and x-ray diffraction techniques, respectively. Implantation was done at room temperature several degrees off <111> axis. One series of samples was implanted with 140 keV He+ at 1.5, 3.0, 4.5, and 6.0×10^15 at. cm^−2. Another series consisted of three profiles obtained with single, double, and triple energies and doses in the range 30–140 keV and 9.0×10^14–3.0×10^15 at. cm^−2. For the highest dose the maximum changes in magnetic properties were: −3200 Oe in uniaxial anistropy Hk, a 55% decrease in magnetization M, a 65% decrease in exchange constant A, a 20% increase in damping parameter alpha, and no change in gyromagnetic ratio gamma. The maximum perpendicular strain epsilon[perpendicular] was 1.26% with a corresponding maximum rms random atomic displacement of 0.23 Å. Lateral strain epsilon|| was zero. No evidence was found for creation of extended defects. The highest dose was, at most, half of that required to produce amorphousness. Both DeltaHk and epsilon[perpendicular] had a significantly sublinear dependence on dose. The ratio of maximum DeltaHk for the 6.0 and 1.5×10^15 at. cm^−2 was 1.8 instead of 4.0. The corresponding ratio for strain was 2.6. The difference in sublinearity indicates that DeltaHk and epsilon[perpendicular] are not linearly related through magnetostriction. The equation relating DeltaHk, M, and epsilon[perpendicular] can be preserved only by invoking implantation-induced changes in Young's modulus, Poisson's ratio, or the magnetostriction.