Spin Seebeck effect in Y-type hexagonal ferrite thin films

Spin Seebeck effect (SSE) has been investigated in thin films of two Y-hexagonal ferrites Ba$_2$Zn$_{2}$Fe$_{12}$O$_{22}$ (Zn2Y) and Ba$_2$Co$_{2}$Fe$_{12}$O$_{22}$ (Co2Y) deposited by a spin-coating method on SrTiO$_3$(111) substrate. The selected hexagonal ferrites are both ferrimagnetic with similar magnetic moments at room temperature and both exhibit easy magnetization plane normal to $c$-axis. Despite that, SSE signal was only observed for Zn2Y, whereas no significant SSE signal was detected for Co2Y. We tentatively explain this different behavior by a presence of two different magnetic ions in Co2Y, whose random distribution over octahedral sites interferes the long range ordering and enhances the Gilbert damping constant. The temperature dependence of SSE for Zn2Y was measured and analyzed with regard to the heat flux and temperature gradient relevant to the SSE signal.Comment: 7 pages, 9 figure

Cluster superconductivity in the magnetoelectric Pb(Fe1/2Sb1/2)O3 ceramics

We report the observation of cluster (local) superconductivity in the magnetoelectric Pb(Fe1/2Sb1/2)O3 ceramics prepared at a hydrostatic pressure of 6 GPa and temperatures 1200-1800 K to stabilize the perovskite phase. The superconductivity is manifested by an abrupt drop of the magnetic susceptibility at the critical temperature TC 7 K. Both the magnitude of this drop and TC decrease with magnetic field increase. Similarly, the low-field paramagnetic absorption measured by EPR spectrometer drops significantly below TC as well. The observed effects and their critical magnetic field dependence are interpreted as manifestation of the superconductivity and Meissner effect in metallic Pb nanoclusters existing in the ceramics. Their volume fraction and average size were estimated as 0.1-0.2% and 140-150 nm, respectively. The superconductivity related effects disappear after oxidizing annealing of the ceramics.Comment: 9 pages, 5 figure

Temperature and thickness dependence of tunneling anisotropic magnetoresistance in exchange-biased Py/IrMn/MgO/Ta stacks

Weinvestigate the thickness and temperature dependence of a series of Ni0.8Fe0.2/Ir0.2Mn0.8 bilayer samples with varying thickness ratio of the ferromagnet/antiferromagnet (tFM tAFM) in order to explore the exchange coupling strengths in tunneling anisotropic magnetoresistance (TAMR) devices. Specific values of tFM tAFM lead to four distinct scenarios with specific electric responses to moderate magnetic fields. The characteristic dependence of the measured TAMR signal on applied voltage allows us to confirm its persistence up to room temperature despite an overlapped contribution by a thermal magnetic noise

FMR and Static Magnetic Properties of Gallium Substituted Magnetoplumbite

Magnetization and uniaxial anisotropy were studied on single crystals of PbFe12-xGaxO19, where x = 0 - 8 from 2 to 360 K. The results suggest that for x > 3 the spin arrangement becomes non-collinear. The magnetic moment and anisotropy for x < 3 are roughly consistent with the random distribution of Ga3+ ions in all sites except for 2b. For x = 5.94 and 8.02 the relatively large anisotropy of the Curie temperature was found. The FMR measurements at T = 300 K were interpred using the g-tensor formulation

Magnetic properties of Pr[Fe(Cn)(6)]·5H(2)O

Magnetic properties of Prussian blue analogues, the molecule-based ferrimagnet Pr[Fe(CN)(6)] - 5H(2)O, are presented. The zero-field-cooled magnetisation curves deviate from the field-cooled magnetisation measurements M(T) below certain temperature T-f = 14.5 K, and show a broad maximum at about T = 12 K. Such a behaviour of M(T) is typical for the small particles system or for non-interacting magnetic clusters. The saturation magnetic moment mu(s) = 2.02 mu(B), determined from M(1/H) curves, agrees very well with the theoretical value. The Curie temperature T-c = 14.8 K were determined from M-2(T) curves. The M(H) curve shows hysteresis behaviour at T = 4.5 K. Magnetic susceptibility chi obeys Curie-Weiss law very well above T = 30 K with mu(eff) = 3.8 mu(B) and theta= -18.6 K. The changes in shapes of low-temperature H-1-solid-echo spectra reflect the changes in the magnetic state of the sample

Magnetooptics in Charge Uncompensated Garnet CaxY3-xFe5O12

The properties of compensating centres in Ca2+ substituted yttrium iron garnet CaxY3-xFe5O12, 0≤ x ≤ 0.39 have been investigated using magnetooptical spectroscopy and magnetization measurements. The Faraday rotation and MCD were measured in the spectral range from 0.5 to 2.5 eV and at temperatures from 6 to 380 K. Different centres were detected and the effects of their localization at low temperatures are discussed

Magnetic Phases In Nanogranular Co-Cu Structures

CoCu nanogranular materials with Co concentration of 5, 9, and 15 at% were produced by annealing the starting melt-spun ribbons at 450° C for 1 h. Their magnetization curves were quantitatively analyzed for the amount of superparamagnetic and ferromagnetic phases in the temperature range of 5-300 K. For the two lower concentrations the majority of particles became already superparamagnetic at these temperatures. The temperature dependence of the AC susceptibility indicated the presence of antiferromagnetic type interactions among the particles