Ya. M. Mukovskii

Origin of high transport spin polarization in La 0.7 Sr 0.3 MnO 3 : Direct evidence for minority spin states

Using the point-contact Andreev reflection technique, we have carried out a systematic study of the spin polarization in the colossal magnetoresistive manganite,

Charge ordering and polaron formation in the magnetoresistive oxide La0.7Ca0.3MnO3

{\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}

Correlation between electroresistance and magnetoresistance in La0.82Ca0.18MnO3 single crystal

(LSMO). Surprisingly, we observed a significant increase in the current spin polarization with the residual resistivity. This counterintuitive trend can be understood as a transition from ballistic to diffusive transport in the contact. Our results strongly suggest that LSMO does have minority spin states at the Fermi level. However, since its current spin polarization is much higher than that of the density of states, this material can mimic the behavior of a true half-metal in transport experiments. Based on our results we call this material a transport half-metal.

Giant microwave magneto‐impedance in a single crystal of La0.7Sr0.3MnO3: The effect of ferromagnetic antiresonance

Neutron scattering has been used to study the nature of the ferromagnetic transition in a single crystal of the perovskite La0. 7Ca0.3MnO3. Diffuse scattering from lattice polarons develops as the Curie temperature is approached from below, along with short range polaron correlations that are consistent with stripe formation. Both the scattering due to the polaron correlations and the anomalous quasielastic component in the magnetic fluctuation spectrum maximize very close to T(C), in a manner remarkably similar to the resistivity, indicating that they have a common origin.

Red Shift of Absorption Edge and Nonmetal–Metal Transition in Single Crystals La1—xSrxMnO3 (x = 0.1, 0.2, 0.3)

The resistivity of La0.82Ca0.18MnO3 single crystal has been investigated as a function of external magnetic field and separately under an applied current flow. The measurements were carried out at various temperatures below and above the ferromagnetic transition temperature TC. It has been found that the dynamic electroresistance exhibits stunning similarities to the colossal magnetoresistance at the corresponding temperatures. The correlation observed between the electric- and magnetic-field effects is attributed to electrically induced magnetoresistance.

Magnetic domains and twin structure of the La0.7Sr0.3MnO3 single crystal

We show that at about 340 K a large (≂50%) change in the microwave absorption of a single crystal of La0.7Sr0.3MnO3 is caused by the application of a field of just a few tens of mT. This large magneto‐impedance occurs at 10 GHz but is absent at 36 GHz, and we demonstrate that these results follow from the frequency and field dependence of the dynamic permeability of a ferromagnetic conductor.

Ferromagnetic resonance in a crystal of La0.7Sr0.3MnO3

The red shift of the fundamental absorption edge (mo.16 eV) of a La 0.9 Sr 0.1 MnO 3 single crystal occurs as the crystal is cooled into the ferromagnetic phase. This result shows that there exist spin-dependent states. The reflection and absorption spectra of La 1-x Sr x MnO 3 single crystals (x = 0.1, 0.2, 0.3) indicate that the red shift may be the reason for the appearance of free charge carriers participating in the colossal magnetoresistance phenomenon. The nonmetal-metal type transition below T C confirms this.

Inherent inhomogeneity in the crystals of low-doped lanthanum manganites

Using a magneto-optical indicator film imaging technique and an x-ray topography, we have observed a strong correlation between magnetic and twin structure of a single crystal of La0.7Sr0.3MnO3 (LSMO). The correlation between magnetic and twin domains can be understood in terms of a rhombohedral deformation of the cubic cell of LSMO which is accompanied by an occurrence of a magnetic anisotropy. Our data and analysis suggest that twin domains play a fundamental role in a low-field magnetization behavior and in magnetotransport properties of LSMO.

SPIN DYNAMICS OF STRONGLY DOPED LA1-XSRXMNO3

A single crystal of La0.7Sr0.3MnO3 was grown by the floating zone method. The ferromagnetic resonance linewidth at 8.5 GHz has a minimum of 50 Oe at 340 K and increases with lowering temperature. This is indicative of some residual inhomogeneity. The anisotropy of the resonance field was studied as a function of angle in the sample plane, and we find a small uniaxial anisotropy, Han≅230 Oe at 77 K.

Magnetic, electric and electron magnetic resonance properties of orthorhombic self-doped La1−xMnO3 single crystals

The X-band electron paramagnetic resonance (EPR) technique and the model analysis of the EPR susceptibility versus temperature were employed to characterize the dopant distribution in a number of La-manganite crystals, low doped with Ca, Sr, and Ba in a La site. Such distribution appears to be inhomogeneous as a result of technological-driven effect. It is emphasized that the above chemical disorder influences strongly both magnetic state and transport of the low-doped manganite crystals.