Microcrystalline Ga1−xMnxN samples with Mn content up to x=0.005 were grown by an ammonothermal method and were studied using various techniques. X-ray diffraction showed characteristic diffraction lines for hexagonal GaN phase mixed with a small contribution (<5%) from the Mn3N2 phase. Raman spectra exhibited characteristic peaks of pure GaN and modes that could be associated with Mn-induced lattice disorder. Electron spin resonance and magnetization measurements were consistent with the dominant Mn2+(d5) configuration of spin S=5/2 which is responsible for the observed paramagnetic behavior of the GaMnN material.

Magnetic circular dichroism (MCD) of a ferromagnetic diluted magnetic semiconductor ${\mathrm{Ga}}_{\text{1−x}}{\mathrm{Mn}}_x\mathrm{As}$ films was measured to clarify their electronic structure. Strong enhancement of MCD by Mn substitution indicated a strong $\mathrm{sp–d}$ hybridization. The $\mathrm{p–d}$ exchange interaction was concluded to be antiferromagnetic, which was in contrast with the reported ferromagnetic $\mathrm{p–d}$ exchange in very diluted paramagnetic GaAs:Mn bulk crystals. The change of the character of the $\mathrm{p–d}$ exchange interaction is due to the unique feature of ${\mathrm{Ga}}_{\text{1−x}}{\mathrm{Mn}}_x\mathrm{As}$ that the relative abundance of the neutral and ionized Mn acceptors controls the $\mathrm{p–d}$ exchange.

The $s,p-d$ exchange interaction of p-type ${\mathrm{Ga}}_{1-x}{\mathrm{Mn}}_x\mathrm{As}\hspace{0.5em}\mathrm{}(x<\mathrm{}0.05\mathrm{})\mathrm{}$ epilayers is investigated by means of magnetoabsorption. The observed ferromagnetic-type splitting of fundamental absorption edge is explained by antiferromagnetic $p-d$ exchange interaction, taking into account the Moss-Burstein effect, resulting from high hole concentration.

The magnetization of Ga1−xMnxN (x<0.1) crystals was measured as a function of the magnetic field and temperature. Paramagnetic behavior typical of spin S=5/2 expected for Mn2+ (d5) magnetic centers was observed in the temperature range of 2 K<T<300 K. On the other hand, antiferromagnetic coupling between Mn ions was clearly visible. The nearest neighbor (NN) coupling constant JNN/kB=−1.9 K was estimated from the temperature dependence of the magnetization.

The magnetic susceptibility and specific heat of the diluted magnetic semiconductor ${\mathrm{Zn}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$Se have been measured in the temperature range 10 mK<T<40 K for 0.01≤x≤0.53. A paramagnetic–spin-glass transition was observed in the whole concentration range. The concentration dependence of the freezing temperature $T_f$ was found to be compatible with a radial dependence of the exchange interaction between manganese ions of the type J(R)∼$R^{\mathrm{-}6.8}$. Based on this observation, we calculated thermodynamic properties with the extended nearest-neighbor pair approximation. It appears that this approximation provides a good simultaneous description of the specific heat and high-field magnetization and reproduces Curie-Weiss temperature for parameters $J_0$/$k_B$=-13 K (nearest-neighbor interaction) and $J_i$(R)/$k_B$=-7/$R^{6.8}$ K (distant-neighbor interaction). A comparison is made with other dilute magnetic semiconductors, and the possible origin of the exchange mechanism is then discussed.