scholarly journals Магнитная анизотропия игольчатых монокристаллических включений MnSb в матрице InSb

Author(s):  
А.И. Дмитриев ◽  
А.В. Кочура ◽  
С.Ф. Маренкин ◽  
E. Lahderanta ◽  
А.П. Кузьменко ◽  
...  

The magnetic anisotropy of needle-like single-crystal MnSb inclusions in the InSb matrix was determined and studied in the temperature range 5 – 350 K. In granular InSb-MnSb samples a power-law dependence of the anisotropy constant K(T) on the saturation magnetization MS(T) is observed in the temperature range 5 – 350 K with an exponent n = 3.2 ± 0.4 in accordance with the theories developed by Akulov, Zener, and Callens.

The five magnetostriction constants h 1 to h 5 have been determined for nickel at 4.2, 77 and 300 K from independent measurements on two crystals. At 4.2 K, h 3 , h 4 and h 5 are all small compared with h 1 and h 2 and there is nothing to suggest that a five-constant equation inadequately represents the magnetostrictive behaviour of nickel at this temperature. Within the temperature range h 3 is positive, implying that the first anisotropy constant, K 1 increases under pressure—in agreement with direct measurements. The combinations h 1 — 1/4 h 3 +5/6 h 4 and h 2 + 1/12 + 2/9 h 5 have been measured at small temperature intervals from 4.2 to 300 K. From these the appropriate combinations of magnetoelastic constants have been determined and their temperature variation compared with the theory of Callen & Callen (1963); agreement is poor. It is concluded that the magnetoelastic constants of nickel do not follow the third power law (nor more general expressions which use the same basis) and that the first anisotropy constant does not obey the tenth power law.


1960 ◽  
Vol 13 (2) ◽  
pp. 196 ◽  
Author(s):  
FD Stacey

It is well known that in most rocks the ferromagnetic fraction occurs as small grains dispersed in a solid, magnetically inert matrix. Recently the magnetic anisotropy of rocks and of chondritic meteorites has been subjected to detailed study by the torque-meter method, and, in an attempt to obtain a physical understanding of the shape and crystal alignments of grains which cause magnetic anisotropy in these natural bodies, a number of artificial specimens have been prepared. Iron, nickel, and magnetite powders were mixed into solidifying media and allowed to set in a cylindrical mould in a 10 kilo-oersted field. The torque curves of the resulting specimens reveal a surprising result. It appears that single crystal magnetic grains tend to string together along lines of forc~, thus producing strongly anisotropic specimens, only when the first magneto crystalline anisotropy constant of the ferromagnetic material is positive.


New values have been obtained for the magnetoelastic coefficients h 3 and h 4 of nickel at room temperature from ferromagnetic resonance experiments on (100) single crystal nickel films. The ratios of h 3 / h 1 and h 4 / h 1 are found to be 0.091 ± 0.007 and 0.153 ± 0.015 respectively which give h 3 = (- 8.5 ± 0.7) x 10 -6 and h 4 = (- 14.3 ± 1.4) x 10 -6 if the Lee & Asgar value of h 3 is used (- 94 x 10 -6 ). The magnetocrystalline anisotropy constant K 1 , the saturation magnetization M and the spectroscopic splitting factor g have been measured also. It is found that K 1 = ( - 5.4 ± 0.3) x 10 4 erg/cm 3 and that g = 2.161 ± 0.009 in agreement with published data on bulk samples but that the value of M is found to be higher than the bulk value by 1.6%. The discrepancies between the values of h 3 , h 4 and M as reported here and the bulk values are discussed. The theory of feromagnetic resonance has been extended to cover the five-constant representation of magnetostriction and to the K 3 anisotropy term. The effect of the g factor having cubic anisotropy on the resonance conditions has been calculated.


2020 ◽  
Vol 4 (1) ◽  
Author(s):  
Yogesh Sharma ◽  
Qiang Zheng ◽  
Alessandro R. Mazza ◽  
Elizabeth Skoropata ◽  
Thomas Heitmann ◽  
...  

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Christian Aermes ◽  
Alexander Hayn ◽  
Tony Fischer ◽  
Claudia Tanja Mierke

AbstractThe knowledge of cell mechanics is required to understand cellular processes and functions, such as the movement of cells, and the development of tissue engineering in cancer therapy. Cell mechanical properties depend on a variety of factors, such as cellular environments, and may also rely on external factors, such as the ambient temperature. The impact of temperature on cell mechanics is not clearly understood. To explore the effect of temperature on cell mechanics, we employed magnetic tweezers to apply a force of 1 nN to 4.5 µm superparamagnetic beads. The beads were coated with fibronectin and coupled to human epithelial breast cancer cells, in particular MCF-7 and MDA-MB-231 cells. Cells were measured in a temperature range between 25 and 45 °C. The creep response of both cell types followed a weak power law. At all temperatures, the MDA-MB-231 cells were pronouncedly softer compared to the MCF-7 cells, whereas their fluidity was increased. However, with increasing temperature, the cells became significantly softer and more fluid. Since mechanical properties are manifested in the cell’s cytoskeletal structure and the paramagnetic beads are coupled through cell surface receptors linked to cytoskeletal structures, such as actin and myosin filaments as well as microtubules, the cells were probed with pharmacological drugs impacting the actin filament polymerization, such as Latrunculin A, the myosin filaments, such as Blebbistatin, and the microtubules, such as Demecolcine, during the magnetic tweezer measurements in the specific temperature range. Irrespective of pharmacological interventions, the creep response of cells followed a weak power law at all temperatures. Inhibition of the actin polymerization resulted in increased softness in both cell types and decreased fluidity exclusively in MDA-MB-231 cells. Blebbistatin had an effect on the compliance of MDA-MB-231 cells at lower temperatures, which was minor on the compliance MCF-7 cells. Microtubule inhibition affected the fluidity of MCF-7 cells but did not have a significant effect on the compliance of MCF-7 and MDA-MB-231 cells. In summary, with increasing temperature, the cells became significant softer with specific differences between the investigated drugs and cell lines.


2006 ◽  
Vol 45 ◽  
pp. 2528-2533 ◽  
Author(s):  
S. Srinath ◽  
N.A. Frey ◽  
H. Srikanth ◽  
G.X. Miao ◽  
A. Gupta

We have investigated the exchange bias in CVD grown epitaxial CrO2/Cr2O3 bilayer thin films using hysteresis loops and resonant RF transverse susceptibility. M-H loops indicated an enhanced coercivity without appreciable loop shift and the transverse susceptibility in CrO2/Cr2O3 bilayers revealed features associated with both the ferromagnetic and antiferromagnetic phases. In addition, TS yielded large anisotropy constant (Keff) values depending on the fraction of Cr2O3 present. The large anisotropy fields observed cannot be accounted for by the variable thickness of CrO2 alone and are indicative of possible exchange coupling between CrO2 and Cr2O3 phases that significantly affects the effective magnetic anisotropy.


2018 ◽  
Vol 536 ◽  
pp. 564-566 ◽  
Author(s):  
Yasuki Kishimoto ◽  
Haruki Matsuno ◽  
Hisashi Kotegawa ◽  
Hideki Tou ◽  
Hiraku Saito ◽  
...  

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