Thermal Hysteresis Control in Fe49Rh51 Alloy through Annealing Process

We report the results of studies of the magnetic and transport properties of Fe49Rh51 alloy prepared by different sequences of quenching and the annealing process. The temperature dependences of the relative initial magnetic permeability and resistivity are analyzed. An optimal regime consisting of annealing at 1300 K for 440 min and quenching from 1300 K to 275 K is found to observe the desired narrow antiferromagnetic–ferromagnetic transition in Fe49Rh51 alloy under cyclic conditions. This has the potential to increase the efficiency of cooling devices based on the magnetocaloric effect of magnetic materials with a first-order field-induced phase transition.

"Effect of Substitution of Positive Ion (M+2) on the Physical Properties of M-Fe2O4 "

"Cobalt, Manganese and Magnesium ferrites powders have been synthesized using chemical mixing method. Calcination and sintering temperatures were 800oC respectively. The characteristics of spinal ferrite have been investigated by XRD technique while the magnetic characterization samples have been done using vibrating sample magnetometer (V.S.M). The magnetic properties such as initial magnetic permeability, quality factor, inductor factor and power loss density are studied under variation of frequency using L.C.R meter as well. Saturation magnetization, coercive field and remanent agnetization are determined from hysteresis loops for all prepared sample.

Self-Propagating High-Temperature Spraying Synthesis of Ferrites Hollow Microspheres

The self-propagating high-temperature spraying synthesis (SHSS) route is evaluated for the synthesis of ferrite powders that are subsequently processed towards the manufacturing of high initial magnetic permeability. The powder samples are used for characterization by SEM, EDS and XRD. The results show that the obtained particles are hollow microspheres from nanometer dimension to several micrometers. The phase structure of hollow microspheres is the mixtures of ferrite and Fe2O3. Permittivity and permeability measurements are made on particles dispersed in a paraffin wax matrix. The microsphere is a ferromagnetic matter with both high magnetic loss and high dielectric loss.

Determination of Initial Magnetic Permeability of YIG Thin Films Using the Current Sheet Method

A new technique of inductive measure to determine the initial magnetic permeability (r) of Yttrium Iron Garnet (YIG) thin films has been conceived and developed in our laboratory. The magnetic material is deposited by radio-frequency sputtering between two copper thin layers on alumina substrate. Because the as-deposited films are amorphous and non magnetic, thermal annealing is necessary to make the films crystallize and to obtain satisfactory magnetic properties. After different tests considering the geometrical, morphological and magnetic properties, we have established a protocol permitting to manufacture a prototype in an original design. The performance of the fabricated micro-inductor has been checked using a physical-chemistry characterization. To obtain accurate measurements, we have used a four-point probe test bench and a precision LCR meter. The current sheet method has been validated with thick layers of commercial YIG. The results obtained for thick and thin films of YIG have been compared to the simulation and theoretical ones. Several tests, made for different thickness and different number of loops, have permitted us to evaluate the magnetic permeability of YIG thin films to 32 ± 4.

Self-Assembled Highly Tunable Magnetoelectric

A magnetoelectric (ME) composite with controlled nanostructures is synthesized using co-assembly of two inorganic precursors with a block copolymer. This solution processed material consists of hexagonally arranged ferromagnetic cobalt ferrite [CoFe2O4, CFO] nano-cylinders within a matrix of ferroelectric lead zirconium titanate [Pb1.1(Zr0.53Ti0.47)O3, PZT] when thin films were prepared by spin coating. The initial magnetic permeability of the self-assembled CFO/PZT nano-composite changes by a factor of five through the application of 2.5 V.