Magnetic mesostructure of giant magnetostrictive spring magnet type multilayers

Chopra, Harsh Deep; Ludwig, Alfred; Quandt, Eckhard; Hua, Susan Z.; Brown, H. J.; Swartzendruber, L. J.; Wuttig, Manfred

doi:10.1063/1.370232

Cited by 8 publications

(5 citation statements)

References 7 publications

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“…Very few investigations of domains in magnetostrictive multilayers are known. Chopra and co-workers [20] showed that in their demagnetized state individual layer of as deposited TbFe/CoFe are single domain due to stray field coupling between adjacent layers. Our measurements and direct observations, on the contrary, show that all layers are connected together by magnetic exchange and the magnetization in the whole stack of the layers turns as a single magnetic vector.…”

Section: +7°fmentioning

confidence: 99%

Magnetostrictive hysteresis of TbCo∕CoFe multilayers and magnetic domains

Jay

Petit

Youssef

et al. 2006

Journal of Applied Physics

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Magnetic and magnetostrictive hysteresis loops of TbCo/CoFe multilayers under field applied along the hard magnetization axis are studied using vectorial magnetization measurements, optical deflectometry and magneto optical Kerr microscopy. Even a very small angle misalignment between hard axis and magnetic field direction is shown to drastically change the shape of magnetization and magnetostrictive torsion hysteresis loops. Two kinds of magnetic domains are revealed during the magnetization: big regions with opposite rotation of spontaneous magnetization vector and spontaneous magnetic domains which appear in a narrow field interval and provide an inversion of this rotation.We show that the details of the hysteresis loops of our exchange-coupled films can be described using the classical model of homogeneous magnetization rotation of single uniaxial films and the configuration of observed domains. The understanding of these features is crucial for applications (for MEMS or microactuators) which benefit from the greatly enhanced sensitivity near the point of magnetic saturation at the transverse applied field.

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Section: +7°fmentioning

confidence: 99%

Magnetostrictive hysteresis of TbCo∕CoFe multilayers and magnetic domains

Jay

Petit

Youssef

et al. 2006

Journal of Applied Physics

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“…The ICC technique is readily able to detect changes in the buried layer, as shown previously in Ref. 9. Other aspects of the ICC method are given elsewhere.…”

Section: Methodsmentioning

confidence: 84%

“…Further results on structure and magnetic behavior are given elsewhere. [5][6][7][8][9] The results on the FePd system are preliminary in nature, and detailed studies will be reported in a later manuscript. The FePd and FePd/ Fe multilayers were deposited by dc magnetron sputtering in Ar pressure ranging from 3 mTorr to 10 mTorr and power from 30 to 120 W. The composition of the FePd films was varied either by sputtering Fe-30 at.…”

Section: Methodsmentioning

confidence: 92%

“…Kneller's exchange-spring mechanism 4 is a striking illustration of how the switching fields can be reduced and strain susceptibility enhanced. [5][6][7][8][9] While Kneller initially described the exchangespring mechanism to develop magnets, exchange coupling can also be used to decrease the switching field, which is proportional to the ratio of anisotropy K to saturation magnetization M s . 10 This is achieved by sandwiching high switching field actuator thin films between high magnetization, soft magnets such as Fe or Fe 50 Co 50 .…”

Section: Introductionmentioning

confidence: 99%

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Magnetoelastic and magnetostatic interactions in exchange-spring multilayers

et al. 2005

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The macroscopic or average aggregate behavior of Kneller's exchange-spring mechanism is well established and widely examined; less is known about its microscopic details. In the present study, the microscopic nature of exchange spring was investigated using TbFe/ FeCo multilayers and correlated with their aggregate behavior ͑magnetostriction, torque, and magnetization curves͒. Results show that, as predicted, the exchange-coupled geometry reduces the switching field by increasing the average magnetization and decreasing the average anisotropy of the multilayers. However, it is the magnetostatic interactions between domain walls in adjacent layers that lead to a reduction in coercivity. Stray fields emanating from domain walls in a given layer magnetostatically lock in with the stray fields from walls in adjacent layers, giving rise to low energy, low coercivity "twin" walls. Since in a multilayer a wall can magnetostatically lock in with walls in layers both above and below it for optimum flux closure, a sharp drop in coercivity is observed when the number of bilayers exceeds two. Preliminary results on Fe-Pd based shape memory alloy ͑SMA͒ thin films and multilayers are also given to further emphasize the efficacy of the exchange-spring mechanism as well as to highlight a key micromagnetic difference between magnetostrictive and magnetic SMA films. In particular, the number of martensite variants is greatly reduced because variants with easy axis normal to the plane of the film are prohibited due to magnetostatic considerations.

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“…A partir da medida da figura 33 foi calculado o coeficiente de magnetostricção do filme de Tb25Fe75 fabricado aplicando a equação 3.1. Os valores assumidos na equação foram ES = 169 GPa, EF = 50 GPa, S = 0,064, F = 0,30 (CHOPRA, et al, 1999) e L = 9.40mm. Os dados foram obtidos na literatura para o substrato de silício com filme amorfo de Tb25Fe75.…”

Section: Medidas De Deflexão Vertical Da Amostra E Cálculo Do Coeficiunclassified

Modelagem e fabricação de modulador em óptica integrada baseado em filme magnetostrictivo para aplicação como magnetômetro.

Lima¹

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The doctoral work aims are the development and simulation of an optical modulator based on the effect of magnetostriction for application as magnetometer. The multiphysics simulations were performed using the Finite Elements Method (FEM). In the manufacturing process of optical modulator integrated optics techniques were applied. The originality of the proposal is based on the construction of an integrated optical waveguide covered by a magnetostrictive film to allow the modulation of the guided wave, through the elasto-optical effect, by the application of external magnetic fields. The applied magnetic field causes deformation of the magnetostrictive material that induces a modification of the stress profile produced in substrate.The substrate has its optical properties altered due to the elasto-optical effect, which causes changes in the properties of transmitted light. The work begins with the study and characterization of Tb25Fe75 and Tb23Co77 magnetostrictive films deposited by sputtering on silicon substrates. A method for sample preparation and measurement of magnetostriction was established. The magnetostrictive coefficient of the films was determined from the direct measurement of displacements of samples by AFM technique for magnetic fields applied. The experimental results obtained allowed to perform MEF simulations to verify the light guided modes generated by the profile of thermally induced stress created by deposition process of magnetostrictive film on B12GeO4 (BGO) substrate. It was also modeled and simulated the effect of the application of magnetic field on the optical guide obtained initially by the effect of thermal stress. In simulation results, it was possible to verify the changes of effective refractive index and optical intensity of guided modes as functions of magnetic fields applied to the modulator. At the end of the work, some prototypes were fabricated. The results of characterizations of the built modulators will allow, in the future, adjustments in simulation models.

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Magnetic mesostructure of giant magnetostrictive spring magnet type multilayers

Cited by 8 publications

References 7 publications

Magnetostrictive hysteresis of TbCo∕CoFe multilayers and magnetic domains

Magnetostrictive hysteresis of TbCo∕CoFe multilayers and magnetic domains

Magnetoelastic and magnetostatic interactions in exchange-spring multilayers

Modelagem e fabricação de modulador em óptica integrada baseado em filme magnetostrictivo para aplicação como magnetômetro.

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