Magnetic properties of single crystalline Ga1−xMnxS have been measured. This material is in the new class of diluted magnetic semiconductors (DMS) based on layered III–VI semiconductors, yet its magnetic behavior is remarkably different from that observed in Ga1−xMnxSe. At 10 K in a 6 T field, the magnetization for an x=0.066 sample has reached ∼10% of the expected saturation magnetization for S=5/2 and remains roughly linear with field where M/H=2×10−5 emu/g G. The prominent broad peak from 119 to 195 K in the magnetization of Ga1−xMnxSe, ascribed to direct Mn–Mn pairs, is absent in our Ga1−xMnxS data. In this temperature range, the magnetization of Ga1−xMnxS is Curie–Weiss like with Jeff/kB≈−50 K. This suggests there are no direct Mn–Mn pairs in the GaS system. However, the magnetization of Ga1−xMnxS does show a sharp cusp at 10.9±0.1 K in fields between 0.0050 and 2 T similar to the spin–glass transition in the II–VI DMS. The Curie–Weiss behavior and cusp at 10.9 K suggest the presence of Mn–S–Mn pairs in the layered III–VI DMS Ga1−xMnxS.
The anisotropic magnetization of the III-VI diluted magnetic semiconductor ͑DMS͒, In 1−x Mn x S, is found within a mixed state model and compared to our measurements. The compound has a markedly different crystal structure from previously investigated III-VI DMS crystals. The singlet portion of the Hamiltonian incorporates the interaction of the incomplete shell of Mn 3d electrons with the crystal lattice within the point-ion approximation. Other terms include the Zeeman, spin-orbit and the spin-spin interactions. The doublet portion of the Hamiltonian assumes the substitutional nearest-neighbor Mn atoms interact with each other via antiferromagnet superexchange coupling. For our samples, the nominal value of x = 2%. The singlet magnetization is found from the energy eigenvalues of the singlet Hamiltonian matrix, which was expressed in terms of an uncoupled angular momentum basis set. Magnetization versus temperature and field results are found for several values of the magnetic field, B, including choices along various directions relative to the underlying lattice. The magnetization was measured over a wide range of temperatures and fields with results compared to the mixed state model, which is an average of the singlet and doublet magnetizations. Overall, the agreement of the theory with the experimental data is excellent except at low temperatures ͑Ͻ Ϸ 10 K͒ where some evidence of possible spin-glass behavior is evident.
Magnetic properties of single crystalline Ga1−xFexSe have been measured. This material is in the new class of diluted magnetic semiconductors based on the III–VI semiconductors. The magnetization versus field for an x=0.05 sample deviates from the linear response seen previously in Ga1−xMnxSe and Ga1−xMnxS and reaches a maximum of 0.12 emu/g (<7% of the expected saturation value) at 1.8 K in 7 T. Ga1−xFexSe exhibits an anisotropy below 2 T from 5 to 400 K with the hard axis perpendicular to the GaSe planes. Neither the broad peak observed from 119–195 K in Ga1−xMnxSe nor the Curie–Weiss behavior observed above 75 K in Ga1−xMnxS are observed in Ga1−xFexSe. The sharp cusp at 10.9 K in Ga1−xMnxS (characteristic of longer range ordering) is also not observed in Ga1−xFexSe in temperatures down to 1.8 K. In 0.1 T in temperatures between 50 and 400 K, the magnetization drops to a roughly constant 0.004 emu/g. Below 5 K, the magnetization approaches a constant value of approximately 0.12 emu/g. The magnetic behavior of Ga1−xFexSe is consistent with Van Vleck paramagnetism.
Results for the anisotropic magnetization of the III-VI diluted magnetic semiconductor ͑DMS͒, In 1−x Mn x S, are presented. The compound has a markedly different crystal structure from previously investigated III-VI crystals. The Hamiltonian includes crystal potential, Zeeman, spin-orbit, and spin-spin terms. The singlet model used assumes that the substitutional Mn are noninteracting which is appropriate when x is small ͑here 2%͒. Magnetization versus temperature results are found for several magnetic fields B. The experimental magnetization is compared to our singlet model results with excellent agreement except at low temperatures ͑ഛ20 K͒ where some evidence of possible spin-glass behavior is evident.
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