Giant change in IR light transmission in La_{0.67}Ca_{0.33}MnO_{3} film near the Curie temperature: promising application in optical devices

Transport, magnetic, magneto-optical (Kerr effect) and optical (light absorption) properties have been studied in an oriented polycrystalline La_{0.67}Ca_{0.33}MnO_{3} film which shows colossal magneto-resistance. The correlations between these properties are presented. A giant change in IR light transmission (more than a 1000-fold decrease) is observed on crossing the Curie temperature (about 270 K) from high to low temperature. Large changes in transmittance in a magnetic field were observed as well. The giant changes in transmittance and the large magneto-transmittance can be used for development of IR optoelectronic devices controlled by thermal and magnetic fields. Required material characteristics of doped manganites for these devices are discussed.Comment: 7 pages, 7 figures, submitted to J. Appl. Phy

Magnetorefractive and Kerr effects in the La0.67Ca0.33MnO3/La0.67Sr0.33MnO3 (n) superlattices

It is demonstrated that in the [La0.67Ca0.33MnO3(d = 9 nm)/La0.67Sr0.33MnO3(9 nm)](3) and [La0.67Ca0.33MnO3(9 nm)/SrTiO3(2 nm)/La0.67Sr0.33MnO3(9 nm)](3) superlattices with the interlayer barriers of nonmagnetic dielectric SrTiO3, the magneto-optical Kerr and magnetorefraction (magnetoreflection and magnetotransmission of unpolarized light) effects have large values close to those for the heterostructures of the same composition. The defects and strain in the layers and at interfaces of superlattices result in appearance of additional band in the Kerr effect spectrum, temperature hysteresis, and abnormal temperature dependence of the Kerr effect. It is shown, that the resonant-like contribution to the magnetoreflection spectra of superlattices is due to the shift of the minima in reflection coefficient near the phonon bands by magnetic field. The increase in magnetotransmission of superlattices relative to a single layered film is due to multiple transmission of light through the layers of superlattices. The intermixing effects at interfaces and deviations of composition of layers from stoichiometry both influence the values of magnetorefraction effect in superlattices and the shapes of their temperature dependences

Effect of an interface boundary on the magnetooptical and magnetotransport properties of La0.67Ca0.33MnO3/La0.67Sr0.33MnO3 heterostructures

The optical, magnetooptical (Kerr effect and magnetotransmission), and magnetotransport properties of La2/3Ca1/3MnO3/La2/3Sr1/3MnO3 and La2/3Ca1/3MnO3/SrTiO3/La2/3Sr1/3MnO3 heterostructures on SrTiO3 substrates are studied. The contribution of the interface boundary to the magnetotransmission is typical of a material with a transitional composition. It is found that a 2-nm-thick SrTiO3 spacer does not influence the shape and position of the magnetotransmission peak in a field normal to the surface of the heterostructure but increases the contribution of the upper layer to the magnetotransmission in the Voigt geometry and also enhances the magnetoresistance that is due to the tunneling of spin-polarized carriers through the spacer. The Kerr spectra taken of the heterostructures are typical of single-layer single-crystal films

Defect-induced high-temperature ferromagnetism in Si

We present a comparative study of the anomalous Hall effect (AHE) and of the transverse Kerr effect (TKE) in the nonstoichiometric $\text{Si}_{1-x}\text{Mn}_x\ (x\approx 0.52\text{--}0.55)$ alloys. The data on AHE and TKE are consistent with each other and clearly indicate the intrinsic above room-temperature ferromagnetic order in the studied samples. We argue that this order is not produced by the phase segregation effects, but rather has a global character, while even a small level of the nonstoichiometry in $\text{Si}_{1-x}\text{Mn}_x\ (x \approx 0.52\text{--}0.55)$ alloys drastically changes their magnetic, electrical, optical and magneto-optical properties as compared to those of the stoichiometric manganese monosilicide MnSi. We propose a qualitative explanation of the obtained experimental results in the frame of the model of defect-induced ferromagnetic order using the first-principles calculations of the electronic and magnetic structure of the system

Magnetorefractive effect in nanostructures, manganites, and magnetophotonic crystals based on these materials

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