Y. H. Hyun

Microstructures and the corresponding magnetic properties of half-doped Nd0.5Sr0.5MnO3 films

The microstructural and magnetic properties of amorphous, nanoclustered, and self-organized bilayer Nd0.5Sr0.5MnO3 films, prepared by rf magnetron sputtering, are investigated. The amorphous film was found to be a typical paramagnet with free motion of the individual Mn spins, and the magnetic properties are well described on the basis of the Curie–Weiss approximation. The nanoclustered film manifests magnetic properties mimicking those of superparamagnetic particles following nonclassical magnetic dynamics. The self-organized bilayer film demonstrates a negative exchange bias typical of a ferromagnet/antiferromagnet hybrid system, in spite of the fact that both layers have a ferromagnetic origin. The magnetic properties of the films are discussed in detail on the basis of modern theoretical models.

Magnetic, magneto-optical, and transport properties of ferromagnetic shape-memory Ni2MnGa alloy

The magnetic, transport, and magneto-optical properties of Ni2MnGa alloy in the martensitic and austenitic states were investigated. The temperature dependence of resistivity shows kinks at the structural and ferroparamagnetic transitions. The temperature dependence of magnetization was also investigated for both the bulk and the film. It was shown that the lack of crystallinity in the amorphous Ni2MnGa alloy films leads to the loss of ferromagnetic order above 4 K. The nature of the interband absorption peaks in the optical-conductivity spectra and in the absorptive part of off-diagonal components of the dielectric function for the authentic state of Ni2MnGa alloy was elucidated.

Evidence for Griffiths phase in La0.4Ca0.6MnO3 film with strip-domain inclusions

The microstructure and the magnetic properties of La0.4Ca0.6MnO3 film, prepared by rf magnetron sputtering on a LaAlO3 substrate, have been investigated. The electron microscopy study reveals the presence of strip-domain phase with a periodic spacing of about 3c for the orthorhombic symmetry. The magnetic measurements show that in addition to the expected antiferromagnetic transition at TN≃120 K with decreasing temperature, the film manifests the Griffiths phase behavior in a wide temperature range.

Griffiths phase and charge ordering in electron-doped La0.9Ce0.1MnO3 films

Microstructural, magnetic, and transport properties of as-deposited La0.9Ce0.1MnO3 films prepared by pulse laser deposition have been investigated. The high-resolution electron-microscopy study reveals that films have a high c-oriented texture with a negligible quantity of CeO2 inclusions. The observed Griffiths-type magnetic behavior above the Curie point and the partial transition of the film into the antiferromagnetic state with decreasing temperature are attributed to the microstructural peculiarities.

Magnetic proximity effect in La0.7Ca0.3MnO3∕La0.9Ca0.1MnO3 multilayer films with diffusive interfaces

The structural, magnetic, and transport properties of La0.7Ca0.3MnO3∕La0.9Ca0.1MnO3 multilayer films prepared by rf-magnetron sputtering are investigated. High-resolution electron-microscopy studies reveal the formation of different crystal structures in the constituent sublayers, but without sharp and well-defined interfaces. At the same time, small regions of double-period modulated phase exist in the La0.9Ca0.1MnO3 sublayers at room temperature, manifesting the formation of a charge-ordered antiferromagnetic state. The magnetic measurements reveal a significant enhancement of the ferromagnetic ordering in the La0.9Ca0.1MnO3 layers due to a strong magnetic coupling between the constituent sublayers. The multilayer films show anisotropic saturation magnetization at low temperature and an alternating shape of the temperature-dependent anisotropic magnetoresistance near the metal-insulator transition.

Magnetic ordering and charge transport in electron–doped La1−yCeyMnO3 (0.1⩽y⩽0.3) films

The microstructure and the magnetic and transport properties of as-deposited La1−yCeyMnO3 (0.1⩽y⩽0.3) films prepared by pulsed laser deposition are investigated in a wide region of temperature and magnetic field. The microstructure analysis reveals that all films have a high c-oriented texture, an orthorhombic crystal lattice, and a negligible quantity of CeO2 inclusions. The observed strip-domain phase with a periodic spacing of about 3c, the crystal lattice of which is the same as for the basic film phase, exhibits magnetic behavior typical for the Griffiths phase. Regions of the double-period modulated phase are found at room temperature in the y=0.1 film, which is interpreted as Mn3+∕Mn2+ ordering with a partial ferromagnetic→antiferromagnetic transition at TN⩽80K. At the same time, the investigation reveals that the magnetic and transport properties of the electron–doped La1−yCeyMnO3 films, driven by cation doping, are similar to those for the hole-doped La∕Ca manganites. Therefore, one can conclude ...