Search results for "magnetostriction"
showing 10 items of 23 documents
Essential Measurements for Finite Element Simulations of Magnetostrictive Materials
2018
We discuss which magnetoelastic material properties are essential to measure in order to model magnetostrictive materials in finite element simulations. We show knowing the magnetic constitutive relation is sufficient, if the elastic behavior without magnetic field is known a priori. We neglect hysteresis, and our starting point is to express the effect of mechanical deformation on the magnetic constitutive relation with a small strain tensor and magnetic flux density. It follows that the (energetic) state of a magnetostrictive material is independent of its history. Then, a certain choice of history allows us to keep magnetism and elasticity distinct. We demonstrate with open source softwa…
Magnetic and magnetoelastic properties of epitaxial (2 1 1)-oriented RFe2 (R=Dy, Tb) thin films
2005
Abstract Epitaxial, (2 1 1)-oriented thin films of RFe 2 (R: rare earth; here: Dy, Tb) were deposited by molecular beam epitaxy on faceted and non-faceted α - Al 2 O 3 ( 1 0 1 ¯ 0 ) (m-plane) substrates utilizing a 15 A thin Fe seed layer and a 500 A Nb buffer layer. Detailed X-ray diffraction analyses revealed a twin-free epitaxial (2 1 1)-oriented growth of buffer layer and film. The magnetostrictive layer RFe 2 , as well as the template layers Nb and Mo exhibited the same crystallographic in-plane orientation with regard to the substrate. The same epitaxial relationship was found for films prepared on faceted and on non-faceted substrates. This implies a coherent crystal overgrowth of th…
Direct imaging of delayed magneto-dynamic modes induced by surface acoustic waves.
2017
The magnetoelastic effect—the change of magnetic properties caused by the elastic deformation of a magnetic material—has been proposed as an alternative approach to magnetic fields for the low-power control of magnetization states of nanoelements since it avoids charge currents, which entail ohmic losses. Here, we have studied the effect of dynamic strain accompanying a surface acoustic wave on magnetic nanostructures in thermal equilibrium. We have developed an experimental technique based on stroboscopic X-ray microscopy that provides a pathway to the quantitative study of strain waves and magnetization at the nanoscale. We have simultaneously imaged the evolution of both strain and magne…
A Magnetostrictive Electric Power Generator for energy harvesting from traffic: Design and experimental verification
2015
In the last decades, the growth in energy demand, the decrease of fossil fuels available in the market and the impact of anthropogenic factors on climate change has given new impulse to research on renewable energy systems, particularly those known as energy harvesting devices (EHDs) [1]. A large number of EHDs have been proposed, using different operating principle [1-4]. Among them, piezoelectric and magnetostrictive seem to be particularly suitable for the application in EHD. In these materials the application of external mechanical stress induces a change in the level of magnetization and therefore an electromotive force (emf) can be generated and collected in order to produce electrica…
Temperature dependence of oxidation behavior and coercivity evolution in fine-grained spinel ferrites
2000
Abstract The present paper reviews for a series of fine-grained MxCoyFe(3−x−y)O4 spinel ferrites (M=Mn, Mo, Cu, V) which oxidize into mixed-valence defect ferrites, a systematic study of the correlation between the oxidation temperature and the variation of coercivity. An increase of the coercivity is observed as often as the oxidation reactions Fe2+→Fe3+ and Mn+→M(n+m)+ (1⩽m⩽3) occur. This enhancement of coercivity has been explained by stresses generated during each specific oxidation reaction. The well-known property of cobalt to strongly magnify the magnetostrictive effects has been used to support this interpretation.
A magnetostrictive sensor interrogated by fiber gratings for DC-current and temperature discrimination
2000
A magnetostrictive sensor head with temperature compensation has been developed for measurement of static magnetic fields. The device consists on two different alloys with similar thermal expansion coefficient one of which has a giant magnetostriction, the expansion of both materials produced by heat and magnetism is detected by two fiber gratings. One of the gratings measures the temperature of the sensor and the difference between the wavelengths reflected by the gratings is a measurement of the magnetically induced strain.
Passive interferometric interrogation of a magnetic field sensor using an erbium doped fiber optic laser with magnetostrictive transducer
2015
Abstract An erbium doped (Er3+) fiber optic laser is proposed for magnetic field measurement. A pair of FBGs glued onto a magnetostrictive material (Terfenol-D rod) modulates the laser wavelength operation when subject to a static or a time dependent magnetic field. A passive interferometer is employed to measure the laser wavelength changes due to the applied magnetic field. A data acquisition hardware and a LabVIEW software measure three phase-shifted signals at the output coupler of the interferometer and process them using two distinct demodulation algorithms. Results show that sensitivity to varying magnetic fields can be tuned by introducing a biasing magnetic field. A maximum error o…
Spontaneous magnetostriction and thermal expansibility of TmFeO3 and LuFeO3 rare earth orthoferrites
2001
Abstract At low temperatures the TmFeO3 orthoferrite shows a strong spontaneous magnetostriction generated by rare earth Tm atoms. This effect essentially depends on the temperature and orientation of the weak ferromagnetism vector of the Fe sublattice and reaches largest values for the directions [1 0 0] and [0 0 1]. The spin reorientation process in TmFeO3 marks itself mainly in the change of the signs of the linear thermal expansion coefficients in the directions mentioned above. Some additional singularities of thermal dependencies of expansion coefficients are observed below 20 K, which may be due to a magnetic compensation effect in the investigated orthoferrite.
Tunable chirped fibre Bragg grating device controlled by variable magnetic fields
2002
A novel dynamic chirping fibre Bragg grating device based on a magnetic field applied to a magnetostrictive transducer capable of tuning its dispersion is presented. Chirping ranges up to 300 ps/nm have been demonstrated, which are suitable for several applications such as tunable transversal filtering and dynamic dispersion compensation.
Ab-initio Calculation of the Properties of Permalloys Used in Electrical Machines
2006
In this paper an ab-initio calculation that allows to describe the main features of permalloys is presented. The calculation is bawd on Korringa-Kohn-Rostoker electronic structure method. The dependence of the magnetocryttalline anisotropy and of the magnetostriction on the concentration of non magnetic addiction is computed.