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Abstract Self‐assembly generated materials induced by an external magnetic field have attracted considerable interest following the development of nanodevices. However, the fabrication of macroscopic and anisotropic magnetic films at the nanoscale remains a challenge. Here, anisotropic magnetic films are successfully prepared using a solution‐based nanowire assembly strategy under a magnetic field. The assembly process is manipulated by changing the thickness of silica shell coated on the surface of magnetic nanowires. The anisotropic magnetic films show highly anisotropic magnetization under different angles of magnetic field and better magnetization properties than that of disordered magnetic films. The well‐defined nanowire arrays enable magnetization anisotropic property which may be useful in the magnetic energy conversion technologies and biomedical sciences which lie far beyond those achievable with traditional magnetic materials.

CoFe nanowires were successfully synthesized in nanoporous anodized aluminum oxide (AAO) template by employing DC electrodeposition process. These nanowires have been electrodeposited in the presence of external magnetic field applied parallel (∥) to the axis of nanowires. The effects of externally applied magnetic field on magnetic and structural properties of CoFe nanowires were investigated. X-ray diffraction (XRD) was used to identify crystal structure of the samples. The XRD pattern indicates polycrystalline nature of Cobalt iron nanowires with Body Centered Cubic (BCC) crystal structure. Scanning Electron Microscopy (SEM) images revealed the uniform growth of nanowires inside the template. To explore the magnetic properties of Cobalt iron nanowires, vibrating sample magnetometer (VSM) was employed. It was revealed that for nanowires electrodeposited with external magnetic field, easy axis of magnetization is found parallel (∥) to the nanowire axis with large variation in anisotropic magnetization. Whereas for nanowires electrodeposited without external magnetic, easy axis of magnetization is perpendicular (⊥) to nanowires axis with small variation in anisotropic magnetization. [ABSTRACT FROM AUTHOR]

Self‐assembly generated materials induced by an external magnetic field have attracted considerable interest following the development of nanodevices. However, the fabrication of macroscopic and anisotropic magnetic films at the nanoscale remains a challenge. Here, anisotropic magnetic films are successfully prepared using a solution‐based nanowire assembly strategy under a magnetic field. The assembly process is manipulated by changing the thickness of silica shell coated on the surface of magnetic nanowires. The anisotropic magnetic films show highly anisotropic magnetization under different angles of magnetic field and better magnetization properties than that of disordered magnetic films. The well‐defined nanowire arrays enable magnetization anisotropic property which may be useful in the magnetic energy conversion technologies and biomedical sciences which lie far beyond those achievable with traditional magnetic materials. [ABSTRACT FROM AUTHOR]

Strong anisotropy is observed in the magnetization and magnetoresistance (MR) of a series of La 0.7 Sr 0.3 MnO 3 (LSMO) films grown on (001) oriented Si using pulsed sputtering plasma. Magnetic anisotropy (MA) of LSMO films is in the order of 106 erg/cm3, comparable to or larger than that of the other heterostructures. Analysis using the Stoner-Wohlfarth model and the density functional theory (DFT) indicates that the crystalline and induced anisotropies are almost compensating with each other, and observed MA is of the same order of shape anisotropy. The rise in MA with the LSMO thickness is attributed to the shape anisotropy and interfacial spin reordering. These LSMO films exhibit positive and negative MR, even though the LSMO is well known for colossal negative MR. The 12.4 nm thick LSMO film shows a maximum ∼7 % in-plane low-field positive MR, which increases to ∼12 % for 20.0 nm thick LSMO, but the variation of out-of-plane positive MR is ∼ ± 0.8 %. The maximum in-plane positive MR occurs at ∼ ± 0.2 kG (switching field), which corresponds to the coercive field. In contrast, the out-of-plane positive MR switching field is relatively higher, ∼ ± 5 kG, 25 times larger than the in-plane switching field. The anisotropy in positive MR and its switching field is due to the strong MA, modulated by the charge transfer-induced interfacial exchange coupling strength, confirmed using the DFT. The MA and anisotropy in MR with the dual sign of MR are intriguing phenomena; their tunability could pave the way for advanced technology in magnetic devices. [Display omitted] • La 0.7 Sr 0.3 Mn O3 (LSMO)/Si shows larger magnetic anisotropy ~ 2.39 x 106 erg/cm3 compared to other reported heterostructures. • LSMO/Si exhibits positive and negative magnetoresistance (MR), even though the LSMO is well known for colossal negative MR. • Variation of in-plane positive MR is 7 to 12 % and ∼±0.8 % along out-of-plane when LSMO thickness changes from 12.4 to 20 nm. • Positive MR switching field for out-of-plane oriented field is 25 times larger than in-plane field, signifying a strong MA. • Strong anisotropic MR and associated large MA of LSMO/Si are attributed to interfacial charge transfer as confirmed by DFT. [ABSTRACT FROM AUTHOR]

Existence of anisotropic Curie temperature materials [E. R. Callen, Phys. Rev. 124, 1373 (1961); J. Appl. Phys. 32, S221 (1961)] is a longstanding prediction - materials that become paramagnetic at a lower temperature along certain crystal directions while remaining magnetically ordered in other directions up to a higher temperature. Validating Callen's theory, we show that all directions within the basal plane of monoclinic Fe7S8 (pyrrhotite) single crystal remain ordered up to 603 K while the c-axis becomes paramagnetic at 225 K. Results prompt a re-evaluation of existing magnetic materials with a focus on magnetic characteristics along different crystal orientations above instead of below the ordering temperatures. Theoretical guidelines for identifying new materials with large anisotropy of Curie temperature are also given, and analysis protocol to characterize them in a self-consistent manner is discussed. Materials with such a large directional dependence of Curie temperature open the possibility for uniquely new devices and phenomena, including (spin) transport. [ABSTRACT FROM AUTHOR]