Nano-composite FePtB thin films were deposited on naturally oxidized (1 0 0) silicon (Si) and glass (SiO2) substrates by using a pulsed laser deposition (PLO) technique. Effects of processing conditions on structural, surface and magnetic properties of the films were examined. Growth temperature (T-s) and the type of substrate (Si or SiO2) are shown to affect crystal structure and magnetic properties of FePtB thin films significantly. Under optimized processing conditions, a similar to 1.7 mu m thick FePtB film deposited on a glass substrate exhibits high coercivity (similar to 7.7 kOe), high reduced remanence [(M-r/M-s) similar to 0.9] and high energy product (BH)(max) = 71 kJ/m(3). The films exhibiting good hard magnetic properties are mainly made-up of nano-sized hard (L1(0)-FePt) and soft (iron-boride) magnetic phases, which are shown to be exchange coupled. Fabrication of hard magnetic thin films by a simple and fast technique such as PLD is very promising for the production of micro magnets for MEMS applications.

Search for novel multi-functional materials, especially multiferroics, which are ferromagnetic above room temperature and at the same time exhibit a ferroelectric behavior much above room temperature, is an active topic of extensive studies today Ability to address an entity with an external field, laser beam, and also electric potential is a welcome challenge to develop multifunctional devices enabled by nanoscience While most of the studies to date have been on various forms of Bi and Ba based Ferrites, rare earth chromites are a new class of materials which appear to show some promise However m the powder and bulk form these materials are at best canted antiferromagnets with the magnetic transition temperatures much below room temperature In this presentation we show that thin films of YbCrO3 deposited by Pulsed Laser Deposition exhibit robust ferromagnetic properties above room temperature It is indeed a welcome surprise and a challenge to understand the evolution of above room temperature ferromagnetism in such a thin film The thin films are amorphous in contrast to the powder and bulk forms which are crystalline The magnetic properties are those of a soft magnet with low coercivity We present extensive investigations of the magnetic and ferroelectric properties, and spectroscopic studies using XAS techniques to understand the electronic states of the constituent atoms in this novel Chromite While the amorphous films are ferromagnetic much above room temperature, we show that any observation of ferroelectric property in these films is an artifact of a leaky highly resistive material

Transformation to Ferromagnetic order above room temperature is observed on amorphizing otherwise antiferromagnetic chromite [Y(Yb)CrO3] thin films produced by pulsed laser deposition.. To understand the underlying physics of this phenomenon, we have combined advanced spectroscopy techniques and first-principles calculations. The amorphization is found to be accompanied by an insulator-metal transition, which in turn affects the magnetic properties. The ferromagnetism (FM) is then explained by evoking a number of coexisting effects, namely disordering of Cr-O-Cr bond angles, metallization which introduces free carriers and the presence of mixed valence states (Cr3+ in the bulk and Cr4+ on the surface). They favor FM coupling through double and direct exchange interactions. Although we have used YCrO3 as case study, our results are more general and must apply for a wide range of oxide systems.

Magnetic and electrical properties have been studied for (Fe72B24Nb4)95.5Y4.5 ferromagnetic thin films fabricated using Pulsed Laser Deposition technique. Magnetic characterization shows that these thin films are soft ferromagnetic at room temperature with high saturating magnetic moment (averaged at 372.5 emu/cc). Magnetic data indicates mixed orientation of magnetic moments where mostly in-plane orientation of magnetic moments along with a minority contribution from out of plane magnetic moments. This arrangement of mixed orientation of magnetic moment is attributed to energy of LASER beam used for deposition. Electrical characterization show peculiar thickness dependence of electrical transport and corresponding optical behavior. Temperature dependence of resistivity shows a negative temperature coefficient of resistance which is characteristic of amorphous state. Mott and Efros-Shklovskii hopping mechanism were found to work under different temperature and thickness regimes for these thin films. Since these thin films are amorphous hence their physical properties are independent of choice of substrate and hence present a major advantage while fabricating magneto-optic devices for NEMS.

Magneto-Optical properties have been investigated for new kind of glassy thin films. 5, 8, 25 and 30 nm (Fe72B24Nb4)95.5Y4.5 thin films were fabricated using Pulsed LASER deposition (PLD) technique. These thin films were then compared to Fe thin films of same thickness deposited under similar conditions. Using inversion of spectroscopic transmittance and reflectance spectra in the wavelength range 300-2500nm, optical constant ε2(imaginary part of dielectric constant) was found. The optical properties resemble those of other transition metals and their alloys, being mainly determined by interband transitions in the studied wavelength range. The free electron contribution is not significant in this region, which is in line with their low electrical conductivity. These thin films also show large moment (~372.5emu/cc) and soft magnetic properties (coercivity of ~15 Gauss). Being glassy in nature, they can be easily fabricated on any kind of substrate and can tolerate high temperatures (Glass transition temperature for bulk material is close to 700°C [1]) without changing physical properties. Epitaxial and defect free growth of thin films are critical parameters for thin film fabrication. These can be avoided using amorphous materials hence (Fe72B24Nb4)95.5Y4.5 thin films has potential for new functional thin film structures and composites for magneto-optic applications.

Robust ferromagnetic ordering at, and well above room temperature is observed in pure transparent MgO thin films (<170 nm thick) deposited by three different techniques. Careful study of the wide scan x-ray photoelectron spectroscopy rule out the possible presence of any magnetic contaminants. In the magnetron sputtered films, we observe magnetic phase transitions as a function of film thickness. The maximum saturation magnetization of 5.7 emu/cm(3) is measured on a 170 nm thick film. The films above 500 nm are found to be diamagnetic. Ab initio calculations suggest that the ferromagnetism is mediated by cation vacancies.

MgO is a widely used material in ceramic and electronic industry. It is a well known insulator which has been used as a spacer layer in electronic circuits and magnetic tunnel junctions. We report room temperature ferromagnetism in undoped, and V doped MgO nanoparticles of the same size (similar to 39 nm diameter) produced by a two-step chemical process, but containing nominal 0.5, 0.7, 0.9, 1, 1.1, and 1.5 at.% V. Strikingly, the saturation magnetization shows an anomalous abrupt increase in its value to 80.2 memu/g for the 1 at% V doped nanoparticles. Also, high resolution TEM studies show that on doping with V the lattice parameters, d(111) in particular, increases from 2.42 angstrom [MgO] to 2.47 angstrom in the case of [MgO:V(1%)]. These results are consistent with recent theoretical predictions on a first principles basis which suggests that the observed ferromagnetism is sensitively dependent on the distance between the V-Mg-V-Mg. Vacancies.