Magnetocrystalline Anisotropy and Twinning Stress of 10M and 2M Martensites in Ni-Mn-Ga System

2006 ◽  
Vol 512 ◽  
pp. 195-200 ◽  
Author(s):  
Nariaki Okamoto ◽  
Takashi Fukuda ◽  
Tomoyuki Kakeshita ◽  
Tetsuya Takeuchi
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Magnetocrystalline Anisotropy ◽  
Anisotropy Constant ◽  
The Other ◽  
Magnetic Shear ◽  
Maximum Value ◽  
Twinning Plane ◽  
Twinning Shear ◽  
The Difference

Ni2MnGa alloy with 10M martensite exhibits rearrangement of martensite variants (RMV) by magnetic field, but Ni2.14Mn0.92Ga0.94 with 2M martensite does not. In order to explain the difference, we measured uniaxial magnetocrystalline anisotropy constant Ku and the stress required for twinning plane movement τreq in these alloys. Concerning the former alloy, the maximum value of magnetic shear stress acting across twinning plane τmag, which is evaluated as |Ku| divided by twinning shear, becomes larger than τr eq. On the other hand, concerning the latter alloy, the maximum of τmag is only one-tenth of τreq at any temperature examined. Obviously, the relation, τmag> τr eq, is satisfied when RMV occurs by magnetic field and vice versa. In this martensite, the large twinning shear of 2M martensite is responsible for small τmag and large τreq.

Influence of Magnetic Field Direction and Temperature on Rearrangement of Martensite Variants in Fe-31.2at.%Pd

2006 ◽  
Vol 512 ◽  
pp. 201-204 ◽  
Author(s):  
Tatsuaki Sakamoto ◽  
Takashi Fukuda ◽  
Tomoyuki Kakeshita
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Magnetocrystalline Anisotropy ◽  
Parent Phase ◽  
Anisotropy Constant ◽  
Orientation Dependence ◽  
Measured Temperature ◽  
Magnetic Field Direction ◽  
Field Orientation ◽  
Twinning Plane

We have measured temperature dependence of the uniaxial magnetocrystalline anisotropy constant Ku and the shear stress τr eq required for the twinning plane movement of an Fe-31.2Pd alloy in order to explain the field orientation dependence of rearrangement of martensite variants (RMV) of this alloy in the field-cooling process. Under the [001]P field (P represents parent phase), the RMV occurs perfectly at the temperatures where the measurement was performed; in this case, the magnetic shear stress acting across the twinning plane τmag, which is evaluated from Ku, becomes nearly twice as large as τr eq. On the other hand, under the [011]P field, the RMV occurs partially at all the measuring temperatures; in this case the maximum of τmag is nearly the same as τr eq. It is successful to evaluate the following relation quantitatively; τmag> τr eq is satisfied when RMV occurs under magnetic field.

Effect of Magnetic Field on Martensitic Transformation Temperature in Ni2MnGa with Single Variant and Multi-Variant States

2007 ◽  
Vol 539-543 ◽  
pp. 3243-3248
Author(s):  
Takashi Fukuda ◽  
Jae Hoon Kim ◽  
Tomoyuki Kakeshita
Keyword(s):  
Magnetic Field ◽  
Transformation Temperature ◽  
Easy Axis ◽  
Magnetocrystalline Anisotropy ◽  
Intermediate Phase ◽  
Martensite Phase ◽  
The Other ◽  
Phase Transformation Temperature ◽  
Martensitic Transformation Temperature ◽  
The Difference

We have studied effect of magnetic field on the martensite (10M) to intermediate phase transformation temperature (As) of Ni2MnGa in order to understand the influence of magnetocrystalline anisotropy on the transformation temperature under a magnetic field. In case of the transformation from multi-variant 10M phase to the intermediate phase, As decreases with increasing magnetic field H for H < 0.8 MA/m, and then it increases on further increasing H. On the other hand, in case of the transformation from the single-variant 10M to the intermediate phase, As increases monotonically with increasing H, where the easy axis of the single variant is parallel to the field direction. The difference between the multi-variant and single variant state can be explained by considering the high magnetocrystalline anisotropy of the martensite phase.

Onset Magnetic Field for Rearrangement of Martensite Variants in Ni2MnGa

2007 ◽  
Vol 561-565 ◽  
pp. 1109-1112
Author(s):  
Takashi Fukuda ◽  
Nariaki Okamoto ◽  
Tomoyuki Kakeshita
Keyword(s):  
Magnetic Field ◽  
Magnetocrystalline Anisotropy ◽  
Spontaneous Magnetization ◽  
Parent Phase ◽  
Anisotropy Constant ◽  
Ferromagnetic Shape Memory Alloy ◽  
Twinning Shear ◽  
Ferromagnetic Shape Memory ◽  
The Magnetic Field ◽  
Good Agreement

The magnetic field strength, Hs, at which rearrangement of martensite variants initiates has been investigated in Ni2MnGa ferromagnetic shape memory alloy by magnetization measurements in the [001]P direction ("P" stands for the parent phase). We have also calculated Hs from the magnetocrystalline anisotropy constant Ku, spontaneous magnetization Ms, twinning shear s and twinning stress τreq by considering the condition for the rearrangement of martensite variants reported previously [Int. J. Appl. Electromagnetics and Mechanics, 23 (2006) 45]. The calculated value of Hs is in good agreement with the experimental value for all the examined temperatures. The agreement confirms the applicability of the reported condition.

Magnetization Process Associated with Rearrangement of Martensite Variants in Iron-Based Ferromagnetic Shape Memory Alloys

2003 ◽  
Vol 785 ◽  
Author(s):  
Takashi Fukuda ◽  
Tatsuaki Sakamoto ◽  
Tomoyuki Terai ◽  
Tomoyuki Kakeshita ◽  
Kohji Kishio
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Magnetization Curve ◽  
Tensile Tests ◽  
Anisotropy Constant ◽  
Ferromagnetic Shape Memory Alloys ◽  
Large Hysteresis ◽  
Twinning Shear ◽  
Magnetic Filed ◽  
Ferromagnetic Shape Memory

ABSTRACTMagnetization processes of Fe-31.2Pd(at.%) and Fe3Pt (S ≈ 0.8) single crystals in martensite state have been examined in order to confirm the propriety of the condition for the rearrangement of variants under magnetic field: τmag>τreq, where τmag is the magnetic shear stress and τreq is the shear stress required for the rearrangement. When the magnetic field is applied along the [001] direction of each specimen, the magnetization curve shows a large hysteresis due to the rearrangement of variants. Its area, i.e., energy dissipation, is nearly the same as that obtained by stress-strain curves, suggesting the path of the rearrangement of variants by magnetic field is essentially the same as that by external stress. From the magnetization curve, the uniaxial magnetocrystalline anisotropy constant Ku is estimated: it is about 350 kJ/m3 for Fe-31.2Pd at 77 K, and is about 500 kJ/m3 for Fe3Pt at 4.2 K. The maximum of τmag, being evaluated from Ku and twinning shear, is about 2.8 MPa for Fe-31.2Pd at 77K and is about 4.3 MPa for Fe3Pt at 4.2K. For Fe-31.2Pd, the value of τreq is obtained by tensile tests at 80 K to be 0.5–2.5MPa, and the above condition is satisfied. The above condition is also confirmed to be adequate by examining the influence of field direction on the magnetic filed-induced strain.

Control of Microstructure Driven by Magnetic Field in Ferromagnetic Intermetallics

2006 ◽  
Vol 980 ◽  
Author(s):  
Tomoyuki Kakeshita ◽  
Takashi Fukuda
Keyword(s):  
Magnetic Field ◽  
Magnetocrystalline Anisotropy ◽  
The Other ◽  
Ferromagnetic Shape Memory Alloys ◽  
Diffusion Controlled ◽  
Twinning Plane ◽  
Solidification Processes ◽  
Ferromagnetic Shape Memory ◽  
Kinetics Of ◽  
The Magnetic Field

AbstractMagnetic field has been known to be effective in solidification processes. Recently, however, it has been revealed that the magnetic field is also effective for controlling the arrangement of variants, which are formed in association with a solid-solid transformation, in some ferromagnetic intermetallic-based alloys with a large magnetocrystalline anisotropy. In this presentation, we will show two of such cases: one is the rearrangement of martensite variants by magnetic field in intermetallic-based ferromagnetic shape memory alloys (Ni2MnGa and Fe3Pt), and the other is formation of mono-variant state by ordering heat-treatment under magnetic field in a L10-type CoPt. The former process is diffusionless and proceeds by the movement of twinning plane under a magnetic field. The latter is a diffusion controlled process. For both the cases, a large magnetocrystalline anisotropy is essentially important for controlling the arrangement of variants, although kinetics of the two processes is quite different each other.

Off-Axis Torsion Tests on Tubular Specimens of Steel

2001 ◽  
Vol 123 (3) ◽  
pp. 268-273 ◽  
Author(s):  
Takenobu Takeda ◽  
Zhongchun Chen
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Maximum Shear Stress ◽  
Torsion Test ◽  
Combined Loading ◽  
Anisotropic Hardening ◽  
Principal Stresses ◽  
Maximum Value ◽  
The Difference ◽  
Tubular Specimens

In order to analyze the anisotropic hardening behavior of metals, an off-axis torsion test by combined loading is developed. In this test, the maximum shear stress direction φ can be changed from 0 deg to 90 deg while the ratio of maximum and minimum principal stresses is kept at −1. With increasing angle φ, the yield stress of the torsional-prestrained steel decreases; the difference between the directions of the maximum shear stress and principal shear strain increment rises to a maximum value and then decreases. It is experimentally verified that anisotropy is more severe when a smaller offset strain is used in defining the yield stress.

FERROMAGNETIC RESONANCE IN TERFENOL-D AT 17 GHz

2001 ◽  
Vol 15 (24n25) ◽  
pp. 3266-3269 ◽  
Author(s):  
G. DEWAR ◽  
S. PAGEL ◽  
P. SOURIVONG
Keyword(s):  
Magnetic Field ◽  
Ferromagnetic Resonance ◽  
Elastic Strain ◽  
Magnetocrystalline Anisotropy ◽  
Anisotropy Constant ◽  
Temperature Range ◽  
Torque Measurements ◽  
The Magnetic Field

Ferromagnetic resonance measurements have been performed on several samples of Terfenol-D ( Dy0.73Tb0.27Fe1.95 ) at 16.95 GHz and over the temperature range 293 to 305 K. We find that the first magnetocrystalline anisotropy constant, obtained from one sample under nearly zero stress, is K1 = (-1.4±1.0)× l06 erg/cm 3 at 294 K. Our measurement is distinct from quasistatic torque measurements in that the lattice does not deform during the measurement and, hence, the anisotropy contribution due to magnetoelastic strain does not enter. The bare anisotropy constant, unmodified by static elastic strain, is [Formula: see text] and [Formula: see text]. The samples exhibited hysteresis; the position of FMR shifted by 4.0 kOe between measurements made with the magnetic field increasing and those made with the field decreasing.

Does draping aeromagnetic data reduce terrain‐induced effects?

Geophysics ◽  
1984 ◽  
Vol 49 (1) ◽  
pp. 75-80 ◽  
Author(s):  
V. J. S. Grauch ◽  
David L. Campbell
Keyword(s):  
Magnetic Field ◽  
Magnetic Behavior ◽  
The Other ◽  
Aeromagnetic Data ◽  
Total Magnetic Field ◽  
Vertical Derivative ◽  
Topographic Features ◽  
Other Hand ◽  
Terrain Effects ◽  
The Difference

Contrary to intuition, draped aeromagnetic surveys (when compared to typical level surveys) amplify, rather than reduce, the problem of magnetic‐terrain anomalies. Calculations of the total magnetic field of various simple magnetic topographies on level and draped surfaces support this conclusion. In cases where draped surfaces are lower than level surfaces, the draped profiles exhibit steeper gradients and deeper polarity lows over topography than do the level profiles. On the other hand, where draped surfaces are higher than level surfaces, all anomalies are attenuated, so that magnetic‐terrain effects might be reduced relative to subsurface sources (depending upon the magnetization of each). The difference in magnetic behavior between level and draped data can be explained by a contribution of a vertical derivative component in the draped case that is absent in the level case. The contribution is most significant near topographic features because both the observation surface and the topographic surface are changing vertically.

Magnetostriction and Hysteresis of Tbdyhofe1.95 Alloys

2012 ◽  
Vol 529 ◽  
pp. 590-593
Author(s):  
Hong Bo Zhang ◽  
Fu Gang Shen ◽  
Tao Yang
Keyword(s):  
Magnetic Field ◽  
Crystal Structure ◽  
Magnetocrystalline Anisotropy ◽  
Anisotropy Constant ◽  
Spin Reorientation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns ◽  
Curie Temperatures ◽  
Curie Temperature Tc

The crystal structure, Curie temperatures, spin reorientation temperature, magnetocrystalline anisotropy constant and magnetostriction of TbDyHoFe1.95 alloys with composition formulation (1-y)Tb0.36Dy0.64Fe1.95+yTb0.20Dy0.22Ho0.58Fe1.95 (0≤y≤1) were investigated. X-ray diffraction patterns demonstrate the TbDyHoFe1.95 alloys possess MgCu2-type cubic Laves structure. The Curie temperature Tc decreases slightly from 381 °C for Tb0.36Dy0.64Fe2 to 379 °C for y=0.3, 375°C for y=0.4 and 373°C for y=0.5. The spin reorientation temperature Tr increases from -94 oC for Tb0.36Dy0.64Fe2 to -70°C for y=0.3 and -51oC for y=0.5. The magnetocrystalline anisotropy constant K1 decreases with increasing y value. The magnetostriction was examined under applied magnetic field H (0

The Propagation of Electromagnetic Waves in a Refracting Medium in a Magnetic Field

1931 ◽  
Vol 27 (1) ◽  
pp. 143-162 ◽  
Author(s):  
D. R. Hartree
Keyword(s):  
Magnetic Field ◽  
Dielectric Constant ◽  
Electromagnetic Waves ◽  
Unit Volume ◽  
The Other ◽  
Stratified Medium ◽  
Dielectric Tensor ◽  
Present Treatment ◽  
Induced Dipole ◽  
The Difference

The equations of propagation of electromagnetic waves, simple harmonic in time, in an optically anisotropic stratified medium are obtained from the treatment of the refracted wave as the resultant of the incident wave and wavelets scattered by the elements of volume of the medium, and are reduced to a simple form.The primitive property of the medium, from which the other optical properties are derived, is the scattering tensor, relating the induced dipole moment per unit volume to the applied electric field.The relation between the dielectric tensor (corresponding to the dielectric constant of an isotropic medium) and the scattering tensor is obtained.A medium consisting of classical oscillators in an external magnetic field is then considered, the scattering tensor and dielectric tensor are evaluated for such a medium, and finally a formula for the refractive index is obtained.For an ionised medium the formula differs from that obtained by Goldstein; the difference is due to the inclusion in the present treatment of a term omitted by Goldstein; the significance of this term is discussed, and its inclusion justified.Taking this term into account makes an important difference to the properties of the medium for long waves; an example is given.

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