ABSTRACT
Room temperature ferromagnetism has been observed in the Cu doped ZnO films deposited under an oxygen partial pressure of 10-3 and 10-5 torr on Pt (200 nm)/Ti (45 nm)/Si (001) substrates using pulsed laser deposition. Due to the deposition at relatively high temperature (873 K), Cu and Ti atoms diffuse to the surface and interface, which significantly affects the magnetic properties. Depth sensitive polarized neutron reflectometry method provides the details of the composition and magnetization profiles and shows that an accumulation of Cu on the surface leads to an increase in the magnetization near the surface. Our results reveal that the presence of the copper at Zn sites induces ferromagnetism at room temperature, confirming intrinsic ferromagnetism.
ABSTRACT
Here we present a study of magnetism in Co_{0.05}Ti_{0.95}O_{2-δ} anatase films grown by pulsed laser deposition under a variety of oxygen partial pressures and deposition rates. Energy-dispersive spectrometry and transmission electron microscopy analyses indicate that a high deposition rate leads to a homogeneous microstructure, while a very low rate or postannealing results in cobalt clustering. Depth resolved low-energy muon spin rotation experiments show that films grown at a low oxygen partial pressure (≈10^{-6} torr) with a uniform structure are fully magnetic, indicating intrinsic ferromagnetism. First principles calculations identify the beneficial role of low oxygen partial pressure in the realization of uniform carrier-mediated ferromagnetism. This work demonstrates that Co:TiO_{2} is an intrinsic diluted magnetic semiconductor.
ABSTRACT
In this manuscript, we reported that the room temperature ferromagnetism was observed in (Zn0.70, Al0.30)O film, which was fabricated by a novel physical method (pulse laser deposition (PLD)). The film was deposited from (Zn0.80, Al0.20)O ceramic target onto quartz (110) substrate by PLD at 400 degrees C under an oxygen partial pressure of 10(-4) torr. TEM result shows ZnO NCs with diameter of 4-5 nm and they are quite uniformly embedded into amorphous ZnO-Al2O3 phase. The SAED shows clearly that ZnO NCs possess polycrystalline structure. The SQUID measurement shows that the film has room temperature ferromagnetism (saturation magnetization = 3.6 emu/cm3) with Curie temperature above 300 K. The magnitude of magnetic moment of the films can be changed by tuning ZnO NCs size. Both oxygen partial pressure and film thickness studies show that the origin of ferromagnetism is possibly related to the oxygen defects at the surface of ZnO NCs.
