Magnetostriction mechanisms

In contrast to the magnetostriction mechanism the spin-orbit coupling is insensitive to the temperature. Experimentally Ai was observed to disappear very rapidly with raised temperature. At the same time the magnon energy diminished so that the A2 gap appeared at the crossing point of MO and TA modes, but with no appreciable reduction in size. Thus, the mixing of MO-TA and MA-TO modes confirms the importance of spin-orbit coupling in the conduction band states of heavy lanthanides. 

This class of smart materials is the mechanical equivalent of electrostrictive and magnetostrictive materials. Elastorestrictive materials exhibit high hysteresis between strain and stress (14,15). This hysteresis can be caused by motion of ferroelastic domain walls. This behavior is more compHcated and complex near a martensitic phase transformation. At this transformation, both crystal stmctural changes iaduced by mechanical stress and by domain wall motion occur. Martensitic shape memory alloys have broad, diffuse phase transformations and coexisting high and low temperature phases. The domain wall movements disappear with fully transformation to the high temperature austentic (paraelastic) phase. 

The two main types of electromechanical transducers are based on either the piezoelectric or the magnetostrictive effect. The more commonly used of which are piezoelectric transducers, generally employed to power the bath and probe type sonicator systems. Although more expensive than mechanical transducers, electromechanical transducers are by far the most versatile and widely used. 

Aside from the A effect which is an interesting feature for designing resonant mechanical devices, MSMM show a GMR (AR) effect (Quandt and Ludwig 1999,2000). Thus, as already introduced in section 3.3, the bending of a magnetostrictive bimorph... 

Various types of the so-called magnetostrictive inchworm type of motor have been proposed and built. A two-leg travelling machine using a magnetostrictive bimorph actuator with 7.5 /zm-thick polyimtde is shown in fig. 86b (Honda et al. 1994 Arai and Honda 1996). In an alternating magnetic field, it can travel in one direction. The maximum speed of approximately 5 mm/s was obtained around the mechanical resonant frequency... 

This class of smart materials is the mechanical equivalent of electrostrictive and magnetostrictive materials. Elastorestrictive materials exhibit high hysteresis between strain and stress. This hysteresis can be caused by motion of fenoelastic domain walls. Tins behavioi is mote complicated and complex near a martensitic phase transformation. 

The practical application of ultrasonics requires effective transducers to change electrical energy into mechanical vibrations and vice versa. Transducers are usually piezoelectric, ferroelectric, or magnetostrictive. The application of a voltage across a piezoelectric crystal causes it to deform with an amplitude of deformation proportional to the voltage. Reversal of the voltage causes reversal of the mechanical strain. Quartz and synthetic ceramic materials are used. 

The magnetostriction constant, Awo, is calculated to be 1870 ppm at 50 K at the magnetic field of 12 T. To calculate this value the elastic constant difference cn - cn was evaluated to be 50 GPa using mechanical properties data [22], The measured value of A100 is very high, comparable to that... 

Due to the second effect the system may reach a percolation threshold and consequently a metal-insulator phase transition may be induced by the magnetic field. It has to be stressed that the contributions to the effective magnetostriction of cobaltites mentioned above have a different dependence on temperature. An increase of temperature induces low-spin to intermediate-spin transitions. At the same time the volume of ferromagnetic clusters decreases with increasing temperature. The competition of these mechanisms leads to the unusual dependence of the effective magnetostriction of cobaltites on temperature. 

The atomic mechanism of magnetostriction is complex. However, two processes can be distinguished at the domain level, which depend on the response of a material to an external magnetic field. The first process involves the migration of domain walls and the second involves the reorientation of domains. The rotation and movement of domains... 

Galvanomagnetic effects and instability of contacts as the reasons for GMR indication were excluded by the great number of measurements under variable conditions. Since the polymer used is quite sensitive to mechanical pressure [4], it is important to study the influence of mechanical factors in magnetic field. The most important factor is the magnetostriction of nickel, because other artefacts can be destroyed by careful experimental performance. 

The kinetics and mechanism of the electrodeposition of indium from acid electrolytes in the presence of an ultrasonic field was studied by Kadyrov and Rakhmatullaev [67] in the early 1980s. They studied the mechanism of the electrodeposition of In from different baths in an ultrasonic field in cells as a means of intensifying the process. They carried out experiments on baths containing various concentrations of Indium (i) In2(S04)3 30g/L, (ii) In2(S04)3 70g/L, (iii) In(N03)3 30g/L, and (iv) InCl3 30 g/L at a pH 2.5 and a temperature of 20 °C. The ultrasonic vibrations were created by a magnetostrictive transducer with frequency of 17.5 kHz fed by a 800-W generator. They found that ultrasound greatly influenced the... 

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