No abstract

In this paper a preparation method for high moment CoFe thin films with soft magnetic properties is reported. A full control of coercivity in a series of 20-nm-thick CoFe films has been achieved without using seed layers, additives, or thermal annealing. The films were sputtered directly onto Si substrates and the coercivity was varied by changing the mean grain size in the sputtered films. The mean grain size was in turn controlled via the sputtering rate. A reduction in the coercivity has been observed from 120Oe for samples with a mean grain size larger than 17nm down to 12Oe for a sample with a mean grain size of 7.2nm. The results are in good agreement with the “random anisotropy model” relating the coercivity to the mean grain size in polycrystalline ferromagnetic films.

No abstract

We report on the measurement of magnetization in melt-textured YBa2Cu307, samples, in the presence of a crossed remnant flux along the c axis, The ab plane magnetization curves become progressively flatter as the magnitude of the remanence increases. The remanence along the G axis decreases as the field in the ab plane increases, and with decreasing remanence the crossed flux magnetization curves merge with the uncrossed one. The c axis remanence is obselved to help in both the entry and exit of the ab plane flux by effectively reducing the pinning barriers. The decrease of the remanence and flux pinning along the ab plane are discussed in terms of rotation and expulsion of flux, and the possibility of flux cutting.

We report giant magnetoelectric coupling at room temperature in a self-assembled nanocomposite of BiFeO3-CoFe2O4 (BFO-CFO) grown on a BaTiO3 (BTO) crystal. The nanocomposite consisting of CFO nanopillars embedded in a BFO matrix exhibits weak perpendicular magnetic anisotropy due to a small out-of-plane compression (∼0.3%) of the magnetostrictive (CFO) phase, enabling magnetization rotation under moderate in-plane compression. Temperature dependent magnetization measurements demonstrate strong magnetoelastic coupling between the BaTiO3 substrate and the nanocomposite film, which has been exploited to produce a large magnetoelectric response in the sample. The reorientation of ferroelectric domains in the BTO crystal upon the application of an electric field (E) alters the strain state of the nanocomposite film, thus enabling control of its magnetic anisotropy. The strain mediated magnetoelectric coupling coefficient α=μodM/dE  calculated from remnant magnetization at room temperature is 2.6 × 10−7 s m−1 and 1.5 × 10−7 s m−1 for the out-of-plane and in-plane orientations, respectively.