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We report on the transport properties of clean, epitaxial Fe(Se,Te) thin films prepared on Fe-buffered MgO (001) single crystalline substrates by pulsed laser deposition. Near Tc a steep slope of the upper critical field for H||ab was observed (74.1 T/K), leading to a very short out-of-plane coherence length, \xi c, of 0.2 nm, yielding 2\xi c(0) approximately 0.4 nm. This value is shorter than the interlayer distance (0.605 nm) between Fe-Se(Te) planes, indicative of modulation of the superconducting order parameter along the c-axis. An inverse correlation between the power law exponent N of the electric field-current density (E-J) curve and the critical current density, Jc, has been observed at 4 K, when the orientation of H was close to the ab-plane. These results prove the presence of intrinsic pinning in Fe(Se,Te). A successful scaling of the angular dependent Jc and the corresponding exponent N can be realized by the anisotropic Ginzburg Landau approach with appropriate \Gamma values 2~3.5. The temperature dependence of \Gamma behaves almost identically to that of the penetration depth anisotropy., Comment: 8 figures

The angular-dependent critical current density, ${J}_{\text{c}}(\ensuremath{\Theta})$, and the upper critical field, ${H}_{\text{c}2}(\ensuremath{\Theta})$, of epitaxial $\text{Ba}{({\text{Fe}}_{1\ensuremath{-}x}{\text{Co}}_{x})}_{2}{\text{As}}_{2}$ thin films have been investigated. No ${J}_{\text{c}}(\ensuremath{\Theta})$ peaks for $H\ensuremath{\parallel}c$ were observed regardless of temperatures and magnetic fields. In contrast, ${J}_{\text{c}}(\ensuremath{\Theta})$ showed a broad maximum at $\ensuremath{\Theta}=90\ifmmode^\circ\else\textdegree\fi{}$, which arises from intrinsic pinning. All data except at $\ensuremath{\Theta}=90\ifmmode^\circ\else\textdegree\fi{}$ can be scaled by the Blatter plot. ${H}_{\text{c}2}(\ensuremath{\Theta})$ near ${T}_{\text{c}}$ follows the anisotropic Ginzburg-Landau expression. The mass anisotropy increased from 1.5 to 2 with increasing temperature, which is an evidence for multiband superconductivity.

Epitaxial hcp cobalt films with pronounced $c$-axis texture have been prepared by pulsed lased deposition either directly onto ${\text{Al}}_{2}{\text{O}}_{3}(0001)$ single-crystal substrates or with an intermediate ruthenium buffer layer. The crystal structure and epitaxial growth relation was studied by x-ray diffraction, pole figure measurements, and reciprocal-space mapping. Detailed vibrating-sample magnetometer analysis shows that the perpendicular anisotropy of these highly textured Co films reaches the magnetocrystalline anisotropy of hcp-Co single-crystal material. Films were prepared with thickness $t$ of $20ltl100\text{ }\text{nm}$ to study the crossover from in-plane magnetization to out-of-plane magnetization in detail. The analysis of the periodic domain pattern observed by magnetic force microscopy allows us to determine the critical minimum thickness below which the domains adopt a pure in-plane orientation. Above the critical thickness the width of the stripe domains is evaluated as a function of the film thickness and compared with domain theory. Especially the discrepancies at smallest film thicknesses show that the system is in an intermediate state between in-plane and out-of-plane domains, which is not described by existing analytical domain models.

The strength of the unidirectional, uniaxial, cubic, and dynamic rotatable anisotropy field together with the effective damping parameter in polycrystalline ${\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}∕\mathrm{Ni}\mathrm{O}$ ferromagnet and/or antiferromagnet systems is studied as a function of NiO thickness and thermal history. A partial transformation of antiferromagnetically induced combined uniaxial and cubic anisotropy to undirectional anisotropy with increasing NiO thickness is confirmed by hysteresis loop modeling. Independent of the occurrence of exchange bias, the overall exchange anisotropy is constant over a wide range of NiO thickness. A reduction of exchange bias with initial annealing is due to a transformation from a fixed to a rotatable antiferromagnetic spin structure, manifesting itself in the appearance of rotatable anisotropy. With annealing at the interface a ${\mathrm{Ni}}_{x}{\mathrm{Fe}}_{y}{\mathrm{O}}_{z}$ layer is formed that changes the interfacial coupling, leading to an additionally enhanced rotatable anisotropy and spin-wave damping. The data imply that the spin structure inside the antiferromagnetic layer is responsible for exchange bias and the dominating contribution to coercivity, the interfacial structure for the overall coupling. The chemical interface structure and the thermomagnetic history are relevant, and have to be taken into account, comparing experimental data with theoretical models of exchange coupling.