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Week interlayer exchange coupling in Fe-Zr and Fe-Ti layered structures

Smardz L., Smardz K.

Materials Science Poland

2006

Vol. 24, No. 3

821--826

20nm-Fe/dZr-Zr/20nm-Fe and 20nm-Fe/dTi-Ti/20nm-Fe trilayers with wedged Zr and Ti sublayers were prepared at room temperature using UHV (5 × 10-10 mbar) RF/DC magnetron sputtering. Results showed that the Fe sublayers are ferromagnetically coupled up to Zr and Ti spacer thickness of about 1.5 and 2 nm, respectively. Furthermore, a weak antiferromagnetic (ferromagnetic) coupling of the Fe sublayers was observed for a Zr (Ti) thickness range between 1.5 and 3 nm (2 and 3.4 nm). The Fe sublayers are very weakly exchange coupled or decoupled for dZr > 3 nm and dTi > 3.4 nm. The small decoupling Ti and Zr thickness could be explained by spontaneous formation of a quasi-amorphous structure of the paramagnetic spacer during the deposition process.

Magnetism and superconductivity in oxide ferromagnet/superconductor heterostructures

Przysłupski P., Tsarou A., Komissarov I., Dybko K., Dłużewski P., Sawicki M., Dąbrowski B., Kimball C.

Materials Science Poland

2006

Vol. 24, No. 3

665--668

We report on the transport and magnetic properties of La0.67Sr0.33MnO3/YBa2Cu3O7/La0.67Sr0.33MnO3 (LSMO/YBCO/LSMO) trilayer structures. The onset of superconducting transition temperature in trilayer structures starts from the sample with 6 nm (5 unit cells) thick YBCO layer. M(H) hystersis loop indicate indirect exchange coupling between LSMO layers across YBCO layer. MR studies demonstrate a change of magnetoconductance (MC) of a trilayer structure with variation of magnetic field, indicating an indirect exchange coupling between LSMO layers across nonsuperconducting YBCO layer.

Structure analysis and local magnetic parameters of magnetoresistance tunnel junctions

Kim C., Kim C. O., Hu Y., Kanak J., Stobiecki T., Ogata S., Tsunoda M., Takahashi M.

Materials Science

2003

Vol. 21, No. 1

9-23

The Magnetoresistance Tunnel Junctions (MTJ) were deposited by DC magnetron sputtering method in the following layer sequence: Ta(50A)/Cu(100A)/Ta(50A)/Ni80Fe20(20A)/Cu(50A)/Mn75Ir25(100A)/Co70Fe30(25A)/Al-O/Co70Fe30(25A)/Ni80Fe20(t) /Ta(50A)/, with t = 0A, 100A and 1000A. X-ray diffraction analysis revealed that highly oriented fcc-(111) of IrMn3, Cu, Ni80Fe20 and Co70Fe30 crystal planes are stacked parallel to the substrate plane. The improvement of (111) texture and crystallinity was observed after annealing. The tunneling magnetoresistance ratio of patterned junction with electrode layer of Ni80Fe20 (t = 1000A), deposited on the free layer of Co70Fe30 (25A) exceeds 40% at room temperature after annealing at 200°C in magnetic field 1kOe. The local hysteresis loops were measured using the magneto-optical Kerr effect system. The relatively irregular variations of coercive force Hc and unidirectional anisotropy field Hua in as-deposited sample are revealed. After 200°C annealing Hc decreases but Hua increases with smooth local variations. Two-dimensional plots of Hc and Hua show the symmetric saddle shapes with their axes aligned with the pinned layer. The distribution of surface roughness is symmetric with respect to the center of MTJ. Correlation between surface roughness and the variation of Hua suggests that the Hua variation of the free layer is well described by dipole interactions in the form of socalled Néel "orange peel" coupling.