Experimental and computational evidence of a surface roughness induced magnetic anisotropy in NiFe thin films coated onto substrates of various surface roughnesses is reported. Magnetic coercive fields of 15 nm NiFe thin films coated on substrates with approximately 7 nm average roughness were remarkably 233% larger than identical thin films coated onto smooth substrates with < 1 nm average roughness. The NiFe films coated onto rough substrates developed hard and easy axes, normally non-existent in NiFe Permalloy. A linear correlation of the incline angles of the hard axis hysteresis loops to the average roughness values of the individual substrates was observed, with 99% correlation level. Using a modified micromagnetics theory that incorporates the effects of surface roughness, it is shown the observed magnetic anisotropy arises due to the spatial anisotropy of the surface roughness, resulting in an effective in-plane uniaxial magnetic anisotropy with energy density up to 15 kJ/m 3 .

We report the experimental and theoretical study of a substrate roughness surface induced magnetic anisotropy in thin films of Fe and Co. The experimental results confirm previously reported data on NiFe thin films and indicate that rough substrates increase the magnetic coercive fields in magnetic thin films. This effect is most prominent in films of thickness comparable to the surface roughness values and materials of small volume magnetic anisotropy. We determined the coercive field of 15 nm Fe thin film sample deposited onto rough PVDF to be 256 Oe, which is more than doubled the value of the coercive field of 15 nm Fe films coated under identical conditions, onto smooth Si substrates. The effect is visible for Co films but weaken by its increased volume magnetic anisotropy. These results are important for applications based on magnetic thin film where the magnetic properties could be adjusted via substrate roughness engineering

Thermally induced generation and annihilation of magnetic chiral skyrmion bubbles and achiral bubbles in Mn-Ni-Ga magnets

We report studies of quasi-remanent polarization states in Pb0.99Nb0.02 [(Zr0.57Sn0.43)0.94Ti0.06]0.98O3 (PNZST) antiferroelectric ceramics and investigation of their relaxation effects using unique in-situ electrically activated time-resolved Synchrotron X-ray powder diffraction (SXPD) and 119 Sn Mössbauer Spectroscopy (MS). The SXPD patterns are consistent with a phase transition from quasi-tetragonal perovskite in 0V relaxed antiferroelectric state to rhombohedral distortion in ferroelectric state under saturating applied voltages of ±2kV. The observed quasi-remanent polarization relaxation processes are due to the fact that tetragonal to rhombohedral distortion does not occur at the applied voltage required to access the quasi-remanent polarization states, and the tetragonal symmetry restored after the removal of the applied electric field is preserved. Since these quasi-remanent polarization states were seen as possibly suitable for memory applications, the implications of this study are that anti-ferroelectrics are more feasible for multi-state dynamic random access memories (DRAM), while their application to non-volatile memories requires development of more sophisticated "read-out" protocols, possibly involving dc electrical biasing.