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The optical absorption and emission spectra, fluorescence kinetics, and radiative and nonradiative transition probabilities of Nd3+ ions in YAlO3 are investigated. Measurements are presented of the energy levels, absorption and emission cross sections, linewidths as a function of temperature and Nd concentration, thermal line shifts, and fluorescence branching ratios. Judd-Ofelt intensity parameters for electric-dipole transition probabilities are derived from measurements of the absorption spectrum. Stimulated emission cross sections, absorption-band intensities, fluorescence quantum efficiency, possible excited-state absorption, and other properties of importance for YAlO3:Nd3+ laser action are discussed.

The magnetic and structural properties of Fe films deposited by ion-beam sputtering (IBS) on (100)-oriented GaAs substrates are described. The films are between 30 and 600 nm thick and are characterized by a coercive field of approximately 3–6 Oe. The saturation magnetization and anisotropy field, inferred from vibrating sample magnetometer measurements agree substantially with the values expected for bulk Fe. Films deposited on the (100) substrate show the expected fourfold (or ‘‘biaxial’’) symmetry with no indication of a uniaxial anisotropy component. These properties make the films ideally suitable for the intended application in a hybrid semiconductor-magnetic memory, in which two magnetic remanent states with mutually orthogonal magnetization directions interact with an electronic flip-flop circuit.

Optical absorption and emission spectra of Cr3+ ions in YAlO3 have been investigated at 300 and 77°K. In the cubic field approximation, the spectra can be fitted by the parameters Dq = 1800 cm−1, B = 590 cm−1, C = 2980 cm−1. An intense vibronic spectrum is associated with 2E → 4A2 fluorescence transitions. Measurements of absorption cross sections and oscillator strengths, thermal broadening and shifts of the R-line fluorescence, and lifetimes of the 2E fluorescence and Cr3+-Cr3+ pair lines are reported. At low temperatures and chromium concentrations, the radiative quantum efficiency of the 2E state is approximately unity. Other relaxation processes become important at temperatures > 400°K. The possibility of observing stimulated emission from YAlO3:Cr3+ is discussed.

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