Awatef Hassini

Transparent Cr-doped SnO2 thin films: ferromagnetism beyond room temperature with a giant magnetic moment

Laser ablated Cr-doped SnO2 thin films grown on various kinds of substrates all show ferromagnetism well beyond room temperature. Surprisingly, films of Sn0.95Cr0.05O2 grown on LaAlO3 substrates have a giant magnetic moment of 6 μB/Cr, which is 20–30 times larger than that of films grown under the same conditions on SrTiO3 and R-cut sapphire substrates. All films are highly transparent.

Ferromagnetism at room temperature with a large magnetic moment in anatase V-doped TiO2 thin films

V-doped TiO2 thin films were grown by laser ablation on LaAlO3 substrates. In the chosen range of the growth conditions, all V:TiO2 films have an anatase structure and exhibit semiconducting and ferromagnetic behaviors at room temperature. V:TiO2 films have a giant magnetic moment and they seem to be far better ferromagnetic than Co/Fe/Ni-doped TiO2 films. This study has proved that a few percent of V substituting for Ti in TiO2 can result in a potential diluted magnetic semiconductor.

Magnetism in V-doped ZnO thin films

Ferromagnetism at room temperature, along with a spin-glass-like behaviour at low temperatures, has been observed in laser ablated V-doped ZnO thin films. It is found that V atoms were well substituted for Zn atoms and resulted in a very uniform distribution among the ZnO matrices.

Fe- and Ni-doped TiO2 thin films grown on LaAlO3 and SrTiO3 substrates by laser ablation

Room temperature ferromagnetic Fe- and Ni-doped TiO2 thin films were grown by the laser ablation on both LaAlO3 and SrTiO3 substrates. Most of the films are pure anatase, and only the films of Ni content of 3.6% and 4.6% are rutile. Films on LaAlO3 substrates are more crystallized than films on SrTiO3 substrates resulting from the lattice mismatch. Our magnetic measurements also suggest that the ferromagnetism in Fe/Ni:TiO2 films is not due to Fe/Ni segregations but due to Fe/Ni:TiO2 matrices.

Co distribution in ferromagnetic rutile Co-doped TiO2 thin films grown by laser ablation on silicon substrates

Pure rutile Co-doped TiO2 films were fabricated by the pulsed-laser-deposition technique on silicon substrates from a ceramic target. Under the right fabrication conditions, Co concentration in the films could be almost the same as in the target, and films under various conditions all are ferromagnetic well above room temperature. Even though Rutherford backscattering spectroscopy measurements show that Co atoms mostly localize near the surface of the films and exist less in deeper levels, other experimental evidence shows that the ferromagnetism does not come from Co segregations, but from the Co-doped TiO2 matrix. Rutile Ti1−xCoxO2 thin films grown by a very simple technique on low-cost silicon substrates showing a Curie temperature (TC) above 400 K appear to be very attractive to applications.

Magnetic properties of V-doped ZnO thin films

Ferromagnetic V-doped ZnO films were fabricated by the conventional pulsed-laser deposition technique on R-cut sapphire substrates from a ceramic target that was made by sol-gel method. All films are highly crystallized to be wurtzite. V-doped ZnO thin films grown at 600–650°C show room-temperature ferromagnetism along with a spin-glass-like behavior at low temperatures. It is found that V atoms were distributed very uniformly in the ZnO matrix. However, different growth conditions could result in different values of the saturation magnetic moment, and an increase of the substrate temperature above 650°C seems to favor a secondary phase, which is antiferromagnetic.

Thermal emittance changes at the charge ordering transition of (Sm0.35Ca0.65)MnO3

The reversible charge ordering transition of (Sm1−x,Cax)MnO3 is associated with strong changes in electrical, magnetic, and infrared properties. In this work, normal spectral emissivity is calculated from infrared reflectance of bulk polished ceramics. Emissivity versus temperature shows a sharp variation at the charge ordering transition near room temperature. By comparing the apparent temperature of the sample with the absolute temperature, we show that Sm0.35Ca0.65MnO3 is a good candidate for infrared furtivity around room temperature.

Ferromagnetic transition-metal-doped tin dioxide thin films

Induced ferromagnetism (FM) above room temperature in Cr/Ni/V-doped SnO/sub 2/ thin films was studied. 200 nm-thick films were grown using pulsed laser deposition technique. Structural study, magnetization measurements and chemical composition determination were done through X-ray diffraction, magnetic force microscopy at room temperature and Rutherford backscattering spectroscopy. Findings prove that doping a small amount of transition metal in nonmagnetic oxides could introduce FM thru Ruderman, Kittel, Kasuya, and Yoshida (RKKY) interaction.