Alteration Of Magnetic Properties Research Articles

Experimental Study of Electromagnetic-Assisted Rare-Earth Doped Yttrium Iron Garnet (YIG) Nanofluids on Wettability and Interfacial Tension Alteration

Applications of nanoparticles (NPs) in the Enhanced oil recovery (EOR) method has become a major research field as nanoparticles are found to be able to interfere with the interfacial tension and wettability of multiphase fluids within the reservoir formation with or without the irradiance of the electromagnetic (EM) waves. For future EOR usage, a material with high temperature stability and low losses under oscillating wave is recommended, Yttrium Iron Garnet (YIG). This paper describes the synthesis of rare-earth doped YIG (RE-YIG, RE = (Lanthanum (La), Neodymium (Nd) and Samarium (Sm)) and the roles of rare-earth in alteration of magnetic properties. These magnetic properties are believed to have direct relation with the change in wettability, viscosity and interfacial tension of YIG nanofluids. Here we prepared the Y2.8R0.2Fe5O12 (R = La, Nd, Sm) NPs using the sol-gel auto-combustion technique and further annealed at 1000 °C for 3 h. The Field Emission Scanning Electron Microscope (FESEM) images reveal the particles having grain size ranging from 100–200 nm with high crystallinity and X-ray Powder Diffraction (XRD) shows varying shift of the peak position due to the bigger size of the rare-earth ions which resulted in structural distortion. The wettability of the nanofluid for all samples shows overall reduction under the influence of EM waves. On the other hand, the interfacial tension (IFT) and viscosity of RE-YIG nanofluids has lower value than the pure YIG nanofluids and decreases when the ionic radius of rare-earth decreases. Sm-YIG has the highest magnitude in IFT and magnetization saturation of 23.54 emu/g which suggests the increase in magnetization might contribute to higher surface tension of oil-nanofluid interface.

Lower Electric Field-Driven Magnetic Phase Transition and Perfect Spin Filtering in Graphene Nanoribbons by Edge Functionalization.

Perfect spin filtering is an important issue in spintronics. Although such spin filtering showing giant magnetoresistance was suggested using graphene nanoribbons (GNRs) on both ends of which strong magnetic fields were applied, electric field controlled spin filtering is more interesting due to much easier precise control with much less energy consumption. Here we study the magnetic/nonmagnetic behaviors of zigzag GNRs (zGNRs) under a transverse electric field and by edge functionalization. Employing density functional theory (DFT), we show that the threshold electric field to attain either a half-metallic or nonmagnetic feature is drastically reduced by introducing proper functional groups to the edges of the zGNR. From the current-voltage characteristics of the edge-modified zGNR under an in-plane transverse electric field, we find a remarkable perfect spin filtering feature, which can be utilized for a molecular spintronic device. Alteration of magnetic properties by tuning the transverse electric field would be a promising way to construct magnetic/nonmagnetic switches.

Magnetic properties and structure of rare-earth-transition-metal thin films implanted with Ar + ions

Changes in the local magnetic properties and structure of amorphous TbFe thin films, induced by ion implantation, have been investigated in comparison with amorphous GdCo thin films. The samples were obtained by rf co-sputtering on glass substrates. X-ray diffraction and Rutherford backscattering spectrometry (RBS) have been used for structural and compositional analysis. Local hysteresis loops and coercive forces were studied by magneto-optic polar Kerr effect. Structural investigations showed the films to be completely amorphous, before as well as after implantation. Magneto-optical measurements pointed to a progressive diminution of local hysteresis loop area and to a specific behaviour of the relative coercive force for TbFe and GdCo samples, with increasing dose. Both effects were explained by the alteration of magnetic properties in the implanted layer.