Magnetoplastic effect: Basic properties and physical mechanisms

Alshits, V. I.; Darinskaya, E. V.; Koldaeva, M. V.; Petrzhik, E. A.

doi:10.1134/1.1612598

Cited by 131 publications

(63 citation statements)

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“…The electron transitions stimulated by magnetic felds may change the local energy of the dislocation interaction with a point defect, which results in plasticization (or hardening [14]) of a number of diamagnetic alkali halide, semiconductor, and metal crystals [10,11]. As was shown earlier, similar processes may also change the rates of chemical reactions in magnetic felds [15,16].…”

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Magnetostimulated changes of microhardness in potassium acid phthalate crystals

2005

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1 The infuence of weak magnetic felds on the mechanical properties of nonmagnetic crystals (magnetoplastic effect) is observed in both micro-[1] and macroplasticity [2][3][4][5][6][7][8][9] and is studied by scientists who use plastic physics methods.The studies started in 1987 [1] showed that the magnetoplastic effect is explained by the action of a magnetic feld on spin-dependent electron transitions either in a system dislocation-paramagnetic center [10,11] or in magnetosensitive complexes of point defects [12,13]. The electron transitions stimulated by magnetic felds may change the local energy of the dislocation interaction with a point defect, which results in plasticization (or hardening [14]) of a number of diamagnetic alkali halide, semiconductor, and metal crystals [10,11]. As was shown earlier, similar processes may also change the rates of chemical reactions in magnetic felds [15,16]. Up to now, the study of the magnetoplastic effect has been performed mainly on isotropic crystals. Interest has arisen in the study of the infuence of a magnetic feld on the properties of nonmagnetic anisotropic crystals with complicated structures widely used in technology.We studied a potassium acid phthalate (KAP) crystal of the composition C 8 H 5 O 4 K with ionic, covalent, and hydrogen bonds [17,18]. An orthorhombic crystal is described by the point symmetry group mm2. The crystal properties are explained by the presence of the polar 001 axis and a large distance between the (010) cleavages (~13 Å). Figure 1 shows the structural formula of KAP crystals possessing piezoelectric properties [19] that are widely used as analyzers in the longwavelength range of the X-ray spectrum and as monochromators in various high-resolution X-ray instruments [20]. In the temperature range from 300 to 2 K, KAP crystals are diamagnetic along all the three main crystallographic directions. SAMPLE PREPARATION AND PROCESSING OF RESULTSThe experimental methods used in our study were selected in accordance with the studies of mechanical properties of KAP crystals [21][22][23] and, in particular, of their microhardness [23]. Motion of dislocations was not studied in any cited works. In [21,22], considerable anisotropy of crystal deformation was observed: depending on the mutual orientation of the compression and polar (z) axes, crystals demonstrated brittle fracture, kink bands, or plastic deformation. To detect the infuence of a magnetic feld on the crystals we used a fast technically simple method of microindentation.The KAP crystals used in our experiments were grown from aqueous solution by the method of decreasing temperature [19] at the Institute of Crystallography of the Russian Academy of Sciences. The samples were cut from crystalline boules by a wet thread. The faces were mechanically polished against a smooth wet silk. Microhardness was measured in the (010) and (100) 2 Magnetic susceptibility of KAP crystals was measured by Yu.G. Shvedenkov at the International Tomography Center, Siberian Division, Russian Academy of Sciences, ...

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Magnetostimulated changes of microhardness in potassium acid phthalate crystals

2005

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“…Different magnetic fields and different apparatus have been adopted to reduce residual stress [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. However, nearly all the researchers study stress changes only after magnetic treatments.…”

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Magnetostriction varieties and stress relief caused by pulsed magnetic field

et al. 2011

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Magnetostriction is investigated to evaluate the stress relief caused by pulsed magnetic field treatment, because this physical property is closely associated with residual stress. Magnetostriction of different stressed samples is measured in this paper. The stress variations caused by pulsed magnetic treatment are also compared. It is found that magnetostriction variations are closely associated with stress changes. Thermodynamic potential is used to find the relationship between them. Based on several assumptions, we find that the product of magnetostriction amplitude and stress magnitude is nearly a constant during magnetic field treatment, which is valuable for stress relief evaluation and optimizing processing parameters. This conclusion is testified by stress measurements, and the calculated values are in accordance with the experiment results.

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“…In our previous works [19,23,7], the plasticization of InSb single crystals under permanent magnetic field was found. It was realized as a preferred motion of the 60 0 dislocations from a scratch ("diverge" half-loops) under the action of a magnetic field at elevated temperatures in the absence of mechanical loading.…”

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confidence: 97%

Magnetostimulated softening and hardening of semiconductors

Darinskaya

Petrzhik

Ivanov

et al. 2005

phys. stat. sol. (c)

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The experiments have been carried out on different compound semiconductors A III B V (InSb) and A II B VI (CdS, CdTe) with sphalerite (InSb, CdTe) and wurtzite (CdS) structure. Two cases of magnetic field influence on mechanical properties of crystals were studied: the variation of properties directly in a magnetic field; and the after-action magnetic effect, in which properties change after a magnetic treatment. It is shown that both softening and hardening of the same crystals can be observed depending on experimental conditions and type of doping. Complex researches of MPE have allowed to attribute it to the range of spin-dependent phenomena determining magnetosensitive interactions between lattice defects. The magnetic field changes a spin state of the crystal defect structure which leads to a removal of a spin forbidding on certain electronic transitions. As a result the local energy of the interaction between defects changes, but the total energy of the system remains practically unchanged. Similar ideas [17,18] provides physical interpretation of the magnetic influence on a number of physical and chemical properties of non-magnetic materials.Some years ago MPE was found out in semiconductors [19] as an enhanced motion of dislocations emitted from a scratch under the action of the magnetic field at elevated temperatures in the absence of mechanical loading. Now the investigations of the magnetic field influence on the mechanical properties and the real structure of semiconductors have been performed by a number of independent groups [19][20][21][22][23][24][25][26][27][28]. They are studying two cases of the magnetic influence: 1) the change of the real structure of crystals directly in the magnetic field (the effect disappears right away after the magnetic field switching off); 2) the change of mechanical properties of crystals after the magnetic treatment (the effect is kept for several days).

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Magnetoplastic effect: Basic properties and physical mechanisms

Cited by 131 publications

References 17 publications

Magnetostimulated changes of microhardness in potassium acid phthalate crystals

Magnetostimulated changes of microhardness in potassium acid phthalate crystals

Magnetostriction varieties and stress relief caused by pulsed magnetic field

Magnetostimulated softening and hardening of semiconductors

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