2009, Rößler, S., Harikrishnan, S., Naveen Kumar, C.M., Bhat, H.L., Elizabeth, S., Rößler, U.K., Steglich, F., Wirth, S.

We report on the magnetic and electrical properties of Pr 0.6Sr 0.4MnO 3 single crystals. This compound undergoes a continuous paramagnetic-ferromagnetic transition with a Curie temperature T C301 K and a first-order structural transition at T S64 K. At T S, the magnetic susceptibility exhibits an abrupt jump, and a corresponding small hump is seen in the resistivity. The critical behavior of the static magnetization and the temperature dependence of the resistivity are consistent with the behavior expected for a nearly isotropic ferromagnet with short-range exchange belonging to the Heisenberg universality class. The magnetization (M-H) curves below T S are anomalous in that the virgin curve lies outside the subsequent M-H loops. The hysteretic structural transition at T S as well as the irreversible magnetization processes below T S can be explained by phase separation between a high-temperature orthorhombic and a low-temperature monoclinic ferromagnetic phase.

2008, Scheerbaum, N., Heczko, O., Liu, J., Hinz, D., Schultz, L., Gutfleisch, O.

Magnetic field-induced twin boundary motion leading to large magnetic field-induced strain of ~1.0% was established in polycrystalline Ni50.9Mn27.1Ga22.0 (at.%) fibres at room temperature (~60–100 μm in diameter and ~3 mm in length). The fibres' grains are as large as the fibre diameter and of random orientation. At room temperature, a ferromagnetic 5M martensite is found. Magnetic field-induced twin boundary motion was indicated by magnetic measurements and validated by electron backscatter diffraction (EBSD). The application of a magnetic field shifts the equilibrium temperature of martensite and austenite by ~0.4 K T−1, which agrees with calculations using the Clapeyron–Clausius approach.

2008, Theis-Bröhl, K., Westphalen, A., Zabel, H., Rücker, U., McCord, J., Höink, V., Schmalhorst, J., Reiss, G., Weis, T., Engel, D., Ehresmann, A., Toperverg, B.P.

A combination of experimental techniques, e.g. vector-MOKE magnetometry, Kerr microscopy and polarized neutron reflectometry, was applied to study the field induced evolution of the magnetization distribution over a periodic pattern of alternating exchange bias (EB) stripes. The lateral structure is imprinted into a continuous ferromagnetic/antiferromagnetic EB bilayer via laterally selective exposure to He-ion irradiation in an applied field. This creates an alternating frozen-in interfacial EB field competing with the external field in the course of the re-magnetization. It was found that in a magnetic field applied at an angle with respect to the EB axis parallel to the stripes the re-magnetization process proceeds via a variety of different stages. They include coherent rotation of magnetization towards the EB axis, precipitation of small random (ripple) domains, formation of a stripe-like alternation of the magnetization, and development of a state in which the magnetization forms large hyper-domains comprising a number of stripes. Each of those magnetic states is quantitatively characterized via the comprehensive analysis of data on specular and off-specular polarized neutron reflectivity. The results are discussed within a phenomenological model containing a few parameters, which can readily be controlled by designing systems with a desired configuration of magnetic moments of micro- and nano-elements.