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The magnetic properties of ceramic La1−xSrxMn1−yFeyO3 samples with x = 0.3 and y = 0.15−0.25 are investigated in magnetic fields of B = 10−103 G at a temperature T between 5−310 K. A ferromagnetic transition at TC, decreasing considerably with y, is accompanied with strong magnetic irreversibility at B = 10 G. The critical behavior of χ (T) ~ (T/TC − 1)−γ is governed at y = 0.15−0.20 by the percolative (γ ≈ 1.8) and Heisenberg (γ ≈ 1.4) spin systems.

Magnetic and galvanomagnetic properties of the group II-V semiconductor CdSb single crystals doped with Ni are reported. The magnetization data give evidence for spheroidal Ni- rich Ni1-xSbx nanoclusters. Mechanism of the low-temperature conductivity is sensitive to the magnetic field, being of the variable-range hopping type in zero field and of the nearest- neighbor hopping type in strong fields. The Hall resistivity contains the normal and the anomalous contributions.

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 < 10-20 K, and MnSb nanoprecipitates responsible for the ferromagnetic (FM) properties of In1-xMnxSb, a superparamagnetic (SP) contribution of atomic-size magnetic Mn complexes (presumably dimers) has been established. The fraction of the MnSb phase, η ∼ 1-4%, as well as the concentration, nsp ∼ (0.8-3.2) × 1019 cm-3, and the magnetic moment of the Mn dimers, μ ∼ 8-9 μB, are determined. The solubility limit of Mn in the InSb matrix, NSL ∼ 1020 cm-3, is estimated. Hysteresis in low (H < 500 Oe) magnetic fields and saturation of the magnetization in high (H > 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. [ABSTRACT FROM AUTHOR]

The structural and transport properties of GaAs/Mn/GaAs/InxGa1-xAs/GaAs quantum wells (x≈0.2) with Mn δ-layer (4–10 at. %), separated from the well by a GaAs spacer, have been studied. The hole mobility in the investigated structures has exceeded the values known for magnetic III-V heterostructures by two orders of magnitude. For structures with the conductivity of the metal type, we have succeeded to observe at low temperatures Shubnikov–de Haas oscillations just confirming the two dimensionality (2D) of the hole energy spectrum. Exactly those 2D holes promote the ferromagnetic ordering of the Mn layer. That has been proven by (i) observing maxima (at 25–40 K) in temperature dependencies of the resistance, which positions agree with calculated values of Curie temperatures (for structures with the indirect interaction of Mn atoms via 2D holes), and (ii) revealing the negative spin-dependent magnetoresistance (NMR) as well as the anomalous Hall effect (AHE), which values are also in good agreement with calculations relating to ferromagnetic 2D III-V systems. As for the structures with the insulator type of the conductivity, their NMR and AHE features evidence the phase separation—the sample fragmentation with the formation of mesoscopic ferromagnetic areas separated by paramagnetic strata of the high tunnel conductivity. [ABSTRACT FROM AUTHOR]

Diluted magnetic semiconductor InSb:Mn exhibits a ferromagnetic behavior up to T ∼ 600 K due to presence of nanosize MnSb precipitates [Kochura et al., J. Appl. Phys. 113, 083905 (2013)]. Transport properties of InSb:Mn, including the resistivity, the magnetoresistance (MR), and the Hall effect, are investigated between T ∼ 1.6 and 300 K in magnetic fields B up to 15 T. The resistivity, ρ( T), displays an upturn with lowering the temperature below T ∼ 10-20 K attributable to the Kondo effect, where the universal Kondo behavior is observed. The Hall resistivity, ρH, demonstrates a nonlinear dependence on B up to T ∼ 300 K, suggesting an anomalous contribution due to the effect of the MnSb nanoprecipitates. The relative MR, Δ ρ( B)/ ρ(0), is positive (pMR) above T ∼ 10 K and transforms into a negative one (nMR) with lowering temperature. The Hall effect and pMR are interpreted simultaneously with the two-band model, addressed to presence of the two types of holes with quite different concentrations and mobilities. The dependences of nMR on B and T follow those of the Khosla-Fischer model, taking into account damping of the spin-dependent scattering of charge carriers in magnetic field. [ABSTRACT FROM AUTHOR]