Underlayer diffusion-induced enhancement of coercivity in high anisotropy FePt thin films

The L1₀ ordered FePt films have been prepared at 300 °C with a basic structure of CrRu/MgO/FePt, followed by a post-annealing process at temperatures from 200 to 350 °C. The magnetic properties and the microstructure of the films were investigated. It is found that coercivity of FePt films increases greatly from 3.57 to 9.1 kOe with the increasing annealing temperature from 200 to 350 °C. The loop slope of the M–H curves decreases with the increasing annealing temperature, which is due to the grain isolation induced by MgO underlayer diffusion during the annealing process. The underlayer diffusion could be a useful approach to prepare the FePt-based composite films for high-density recording media.     

Substrate influence on the structure of thin films

A Mössbauer spectroscopic study of the influence of the substrate on the structure of FeTe thin films has indicated the possibility of controlling the film structure by suitably modifying the substrate.     

Observation of reversed hysteresis loops and negative coercivity in CoFeAlO magnetic thin films

The magnetic and magneto-optical properties of CoFeAlO thin films fabricated by the RF magnetron reactive sputtering technique have been studied via vibrating sample magnetometer and the magneto-optical Kerr effect. It is found that, along the hard magnetization direction, the magnetic hysteresis loop is reversed and the coercive force is negative. This phenomenon can qualitatively be interpreted within the framework of the proposed two-layers model. It was also found that when as-deposited CoFeAlO thin films were annealed in vacuum (2×10⁻⁷ Torr) at a temperature of 180 °C for 2 h, the negative coercivity disappeared. The relationship between the magnetic and microstructural behaviors of the thin films is discussed.     

Ultra large coercivity in barium ferrite thin films prepared by magnetron sputtering

Hexagonal barium ferrites were deposited onto sapphire substrates by radio frequency magnetron sputtering. The composition, microstructure, and magnetic properties of these isotropic thin films were investigated with Rutherford backscattering spectroscopy, X-ray diffraction, atomic force microscopy, magnetic force microscopy and SQUID magnetometry. The intrinsic coercivity of the films reaches about 11.5 kOe at room temperature. The mechanism of the coercivity is proposed to be nucleation in the decoupled single domain nanometer particles as shown by the characteristics of the magnetic domains and the virgin magnetization curves.     

Structural influence on the 2D-conductivity of thin Au films

Thin gold films (60Å–500Å) are prepared simultaneously onto carbon coated quartz- and NaCl-crystals at different substrate temperatures (5 KT300 K) in uhv. For the Au-films condensed onto the quartz substrates the temperature dependence of the electrical resistivity is measured between 1.7 K and 300 K in situ. The corresponding Au-films condensed onto NaCl are removed and investigated in an EM. The observed hole and channel structures are related to the 2D-conductivity behavior.Dedicated to B. Mühlschlegel on the occasion of his 60th birthday     

The influence of dielectric films on the superconductivity of thin Sn and Tl films

The change in transition temperature for thin Sn and Tl films has been measured after deposition of dielectric substances. The change in transition temperature is inversely proportional to the thickness of the superconducting film and relatively independent of the thickness of the dielectric film. When SnS or Tl₂Se is deposited on Sn films, the transition temperature is depressed. When TICl or Tl₂Se is deposited on Tl films, the transition temperature is increased. When S is deposited on Tl films, there is no initial change inT _c ; however,T _c is appreciably increased after annealing. A possible explanation for this effect is the reduction of the free electron concentration in the metal through the formation of the contact potential between the dielectric and the metal.     

附着铜膜的内应力及屈服强度

用X-射线衍射和热循环基片弯曲方法测量了附着在基体上纯铜膜的内应力和屈服强度。内应力为张应力且随工作气体（氩气）压强的增加而减小但随膜厚的增加而增加。钢基体上铜膜的张屈服强度与膜厚的倒数成反比。压屈服强度也同样依赖于膜厚，即膜越薄，压屈服强度越高。     

Composition influence on the microstructures and magnetic properties of FePt thin films

The Fex Pt 100x (10nm) (x=31-51) thin films are fabricated on Si (100) substrates by using magnetron sputtering. The highly ordered L1 0 FePt phase is obtained after post-annealing at 700℃in Fe 47 Pt 53 thin film. The sample shows good perpendicular anisotropy with a square loop and a linear loop in the out-of-plane and the in-plane direction, respectively. The variations of the magnetic domains are investigated in the films when the content value of Fe changes from 31% to 51%.     

Magnetic properties and microstructure study of high coercivity Au/FePt/Au trilayer thin films

High-coercivity Au(60 nm)/FePt(δ nm)/Au(60 nm) trilayer samples were prepared by sputtering at room temperature, followed by post annealing at different temperatures. For the sample with δ=60 nm, L1₀ ordering transformation occurs at 500 °C. Coercivity (H_c) is increased with the annealing temperature in the studied range 400–800 °C. The H_c value of the trilayer films is also varied with thickness of FePt intermediate layer (δ), from 27 kOe for δ=60 nm to a maximum value of 33.5 kOe for δ=20 nm. X-ray diffraction data indicate that the diffusion of Au atoms into the FePt L1₀ lattice is negligible even after a high-temperature (800 °C) annealing process. Furthermore, ordering parameter is almost unchanged as δ is reduced from 60 to 15 nm. Transmission electron microscope (TEM) photos indicate that small FePt Ll₀ particles are dispersed amid the large-grained Au. We believe that the high coercivity of the trilayer sample is attributed to the small and uniform grain sizes of the highly ordered FePt particles which have perfect phase separation with Au matrix.     

The influence of the substrate on the Debye-Waller factor of very thin films

The temperature dependence of the Debye-Waller factor of very thin undisturbed films is studied. It is found that if interaction between the substrate and the film does not exist the Debye-Waller factor diverges, with the exception of the case of zero absolute temperature, so that under these conditions resonance recoilless absorption and emission of X- and-rays or neutrons by the nucleus of the film cannot occur. In the presence of interaction between the film and substrate the Debye-Waller factor is finite; its temperature dependence was determined.     

Effect of stress in copper ferrite thin films

Cubic copper ferrite thin films, obtained by rf sputtering on quartz and subsequent post-annealing and quenching, show a large coercivity of about 300–600 Oe. Stress measurements using X-ray diffraction show high value of stress of about 400–1000 MPa. Both the stress and coercivity are found to increase with the decrease of the thickness of the films. There appears to be a contribution of the stress to the coercivity of the films, in the in-plane M–H loops.     

Magnetic domain wall pinning and coercivity in FePt/MgO and FePt/Pt thin films

FePt thin layers have been epitaxied either on Pt(0 0 1) or on MgO(0 0 1) substrates, and magnetically characterized using extraordinary Hall effect magnetometry and magnetic force microscopy. The coercivity originates in both cases from the pinning of domain walls on structural defects. Whereas the coercivity increases with the FePt layer thickness in FePt/Pt samples, it decreases in FePt/MgO samples. This discrepancy is explained on the basis of structural observations, and of atomistic simulations of magnetic domain wall pinning.     

Residual stress in Ni-Mn-Ga thin films deposited on different substrates

Four series of Ni_51.4Mn_28.3Ga_20.3/substrate thin film composites, where the substrate is either Si(100), MgO(100), alumina or Mo foil, and two series of Ni_53.5Mn_23.8Ga_22.7/substrate composites where the substrate is either alumina or Mo foil, with different film thicknesses varying from 0.1 to 5 μm have been studied in the cubic phase by XRD stress measurements. The values of residual stresses are found to be dependent on both substrate and film thickness. In the submicron range, a correlation between thickness dependencies of residual stress and transformation temperatures is experimentally obtained. The temperature dependence of the d-spacing d₂₂₀ is studied for the films deposited on Si(100).     

The influence of the structure of thin antimony films on their electrical conductivity

The eletrical conductivity of antimony films of different thicknesses was studied at different temperatures. For small thicknessd, whereL is the electron mean-free path, the film resistances varies asd ^?n , wheren=2. However, ford?L the value ofn becomes smaller than 2 which is in agreement with the theory.     

In-plane magnetization with high coercivity in terbium iron garnet thin films deposited on Pt/Si substrate by PLD

We report on the growth of terbium iron garnet (TbIG, Tb₃Fe₅O₁₂) thin films having anomalously large coercivity and in-plane easy axis of magnetization. The TbIG thin films were prepared at room temperature (RT) on Pt/Si(1 0 0) substrates by pulsed laser deposition technique. The films deposited at RT were X-ray amorphous and do not show any magnetic order. Annealing of the RT deposited film at 900 °C resulted into fully textured (532) TbIG film. Atomic force microscopy and cross-sectional scanning electron microscopy studies of the TbIG films showed good surface quality with an average surface roughness of 5.0 nm and thickness of about 300 nm, respectively. The M-H loops measured at 20 K for TbIG films, exhibit about an order of magnitude enhancement in the coercivity value (H_c) than the single crystal. In-plane and out-of-plane M-H loops revealed that the easy axis of the magnetization lies within the film’s plane. In-plane magnetization combining with large H_c value of the TbIG thin film may be of scientific interest for the possible applications.