Structural and magnetic properties of In1-xMnxSb: Effect of Mn complexes and MnSb nanoprecipitates

Structural and magnetic properties of the group III-V diluted magnetic semiconductor In1−xMnxSb with x = 0.005–0.06, including the nuclear magnetic resonance (NMR) investigations, are reported. Polycrystalline In1−xMnxSb samples were prepared by direct alloying of indium antimonide, manganese and antimony, followed by a fast cooling of the melt with a rate of 10–12 K/s. According to the X-ray diffraction data, part of Mn is substituted for In, forming the In1−xMnxSb matrix. Atomic force microscopy and scanning tunneling microscopy investigations provide evidence for the presence of microcrystalline MnSb inclusions (precipitates), having a size of ∼100–600 nm, and the fine structure of nanosize grains with a Gaussian distribution around the diameter of ∼24 nm. According to the NMR spectra, the majority of Mn enters the MnSb inclusions. In addition to the single Mn ions, which contribute to the magnetization M (T) only in the low-temperature limit of T 20 kOe) magnetic fields are observed, indicating a presence of the SP and FM contributions to the dependence of M (H) up to T ∼ 500 K. The hysteresis is characterized by the coercivity field, Hc, decreasing between ∼100 and 75 Oe when T is increased from 5 to 510 K. The values of Hc are in reasonable agreement with the effect of the largest MnSb inclusions. The maximum of M (T), measured in the zero-field-cooled and the field-cooled conditions in a weak field of 500 Oe, is observed at T ∼ 510 K and is attributable to the Hopkinson effect