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Full-Text Articles in Physics

Tetragonal Magnetostriction And Magnetoelastic Coupling In Fe-Al, Fe-Ga, Fe-Ge, Fe-Si, Fe-Ga-Al, And Fe-Ga-Ge Alloys, J. B. Restorff, M. Wun-Fogle, K. B. Hathaway, A. E. Clark, Thomas A. Lograsso, G. Petculescu Jan 2012

Tetragonal Magnetostriction And Magnetoelastic Coupling In Fe-Al, Fe-Ga, Fe-Ge, Fe-Si, Fe-Ga-Al, And Fe-Ga-Ge Alloys, J. B. Restorff, M. Wun-Fogle, K. B. Hathaway, A. E. Clark, Thomas A. Lograsso, G. Petculescu

Ames Laboratory Publications

This paper presents a comparative study on the tetragonal magnetostriction constant,λγ,2, [ = (3/2)λ100] and magnetoelastic coupling, b1, of binary Fe100-xZx (0 < x < 35, Z = Al, Ga, Ge, and Si) and ternary Fe-Ga-Al and Fe-Ga-Ge alloys. The quantities are corrected for magnetostrains due to sample geometry (the magnetostrictive form effect). Recently published elastic constant data along with magnetization measurements at both room temperature and 77 K make these corrections possible. The form effect correction lowers the magnetostriction by ∼10 ppm for high-modulus alloys and by as much as 30 ppm for low-modulus ...


Flux Growth At Ambient Pressure Of Millimeter-Sized Single Crystals Of Lafeaso, Lafeaso1−Xfx, And Lafe1−Xcoxaso, J.-Q. Yan, Shibabrata Nandi, Jerel L. Zarestky, W. Tian, Andreas Kreyssig, Brandt A. Jensen, A. Kracher, Kevin W. Dennis, Robert J. Mcqueeney, Alan I. Goldman, R. William Mccallum, Thomas A. Lograsso Dec 2009

Flux Growth At Ambient Pressure Of Millimeter-Sized Single Crystals Of Lafeaso, Lafeaso1−Xfx, And Lafe1−Xcoxaso, J.-Q. Yan, Shibabrata Nandi, Jerel L. Zarestky, W. Tian, Andreas Kreyssig, Brandt A. Jensen, A. Kracher, Kevin W. Dennis, Robert J. Mcqueeney, Alan I. Goldman, R. William Mccallum, Thomas A. Lograsso

Ames Laboratory Publications

Millimeter-sized single crystals of LaFeAsO, LaFeAsO1−xFx, and LaFe1−xCoxAsO were grown in NaAs flux at ambient pressure. The detailed growth procedure and crystal characterizations are reported. The as-grown crystals have typical dimensions of3×4×0.05–0.3 mm3 with the crystallographic c-axis perpendicular to the plane of the platelike single crystals. Various characterizations confirmed the high quality of our LaFeAsO crystals. Co and F were introduced into the lattice leading to superconductingLaFe1−xCoxAsO and LaFeAsO1−xFx single crystals, respectively. This growth protocol ...


Influence Of Annealing And Phase Decomposition On The Magnetostructural Transitions In Ni50mn39sn11, William M. Yuhasz, Deborah L. Schlagel, Qingfeng Xing, Kevin W. Dennis, R. William Mccallum, Thomas A. Lograsso Feb 2009

Influence Of Annealing And Phase Decomposition On The Magnetostructural Transitions In Ni50mn39sn11, William M. Yuhasz, Deborah L. Schlagel, Qingfeng Xing, Kevin W. Dennis, R. William Mccallum, Thomas A. Lograsso

Ames Laboratory Conference Papers, Posters, and Presentations

Magnetic and structural transitions in the Ni50Mn50−xSnx (x = 10–25) ferromagnetic shape memory alloys are currently of interest. As in Ni–Mn–Ga, these alloys feature high-temperature austenite and low-temperature martensite phases, where the magnetic state is strongly composition dependent. To study the role of chemical ordering in fine-tuning their magnetostructural properties, they were first annealed for 4 weeks/1223 K to achieve structural and compositional homogeneity, and were then further annealed for 1 week ( ∼ 150 K below the reported B2 to L21 transition) at 773 K to increase the degree ...


Magnetostriction Of Ternary Fe–Ga–X (X = C,V,Cr,Mn,Co,Rh) Alloys, A. E. Clark, J. B. Restorff, M. Wun-Fogle, K. B. Hathaway, Thomas A. Lograsso, Mianliang Huang, E. Summers Apr 2007

Magnetostriction Of Ternary Fe–Ga–X (X = C,V,Cr,Mn,Co,Rh) Alloys, A. E. Clark, J. B. Restorff, M. Wun-Fogle, K. B. Hathaway, Thomas A. Lograsso, Mianliang Huang, E. Summers

Ames Laboratory Conference Papers, Posters, and Presentations

Binary iron-gallium (Galfenol) alloys have large magnetostrictions over a wide temperature range. Single crystal measurements show that additions of 2 at. % or greater of 3d and 4d transition elements with fewer (V, Cr, Mo, Mn) and more (Co, Ni, Rh) valence electrons than Fe, all reduce the saturation magnetostriction. Kawamiya and Adachi [J. Magn. Magn. Mater. 31–34, 145 (1983)] reported that the D03 structure is stabilized by 3dtransition elements with electron∕atom ratios both less than iron and greater than iron. IfD03 ordering decreases the magnetostriction, the maximum magnetostriction should ...


Magnetostrictive And Magnetoelectric Behavior Of Fe–20 At. % Ga/Pb(Zr,Ti)O3 Laminates, Shuxiang Dong, Junyi Zhai, Feiming Bai, Jiefang Li, D. Viehland, Thomas A. Lograsso Apr 2005

Magnetostrictive And Magnetoelectric Behavior Of Fe–20 At. % Ga/Pb(Zr,Ti)O3 Laminates, Shuxiang Dong, Junyi Zhai, Feiming Bai, Jiefang Li, D. Viehland, Thomas A. Lograsso

Ames Laboratory Publications

The magnetostrictive and magnetoelectric (ME) properties of laminate composites of Fe–20 at. % Ga and Pb(Zr,Ti)O3 (PZT) have been studied for laminates of different geometries. The results show that (i) a long-type magnetostrictive Fe–20 at. % Ga crystal plate oriented along 〈001〉c and magnetized in its longitudinal (or length) direction has higher magnetostriction than a disk-type one; and consequently (ii) a long-type Fe–20 at. % Ga/PZT laminate has a giant ME effect, and is sensitive to low-level magnetic fields.


Dynamics Of The Magnetic Field-Induced First Order Magnetic-Structural Phase Transformation Of Gd5(Si0.5ge0.5)4, J. Leib, J. E. Snyder, Thomas A. Lograsso, Deborah L. Schlagel, David C. Jiles Jun 2004

Dynamics Of The Magnetic Field-Induced First Order Magnetic-Structural Phase Transformation Of Gd5(Si0.5ge0.5)4, J. Leib, J. E. Snyder, Thomas A. Lograsso, Deborah L. Schlagel, David C. Jiles

Ames Laboratory Conference Papers, Posters, and Presentations

The system Gd5(SixGe1−x)4 for 0.4⩽x⩽0.5 has been shown to have an unusual first order, coupled magnetic-structural phase transformation at the Curie temperature. Above the transformation temperature Tc, the material is paramagnetic with a monoclinic structure; below Tc, it is ferromagnetic with an orthorhombic structure. Another unusual feature of this phase transformation is that an applied magnetic field can increase Tc by 5 K per tesla. In this study, the magnetic-structural transformation in single crystalGd5Si2Ge2 was triggered by holding the sample at ...


Magnetism, Elasticity, And Magnetostriction Of Fecoga Alloys, Liyang Dai, James Cullen, Manfred Wuttig, Thomas A. Lograsso, Eckhard Quandt May 2003

Magnetism, Elasticity, And Magnetostriction Of Fecoga Alloys, Liyang Dai, James Cullen, Manfred Wuttig, Thomas A. Lograsso, Eckhard Quandt

Ames Laboratory Publications

It is known that the substitution of Co for Fe gives rise to increases in magnetization and Curie temperature, not only in the bcc metals, but also in intermetallic compounds and alloys as well. With the expectation that this is the case in Co-substituted FeGa, we measured magnetization, Curie temperature, magnetostriction and elastic constants of a series of polycrystalline FeCoGa ternary alloys with up to 17% Ga and up to 10% Co. The magnetostriction at saturation for Fe0.93−xCo.07Gax increases to 90 ppm for x=0.17. For larger percentages of Co, the rise ...


Temperature And Stress Dependencies Of The Magnetic And Magnetostrictive Properties Of Fe0.81ga0.19, R. A. Kellogg, Alison B. Flatau, A. E. Clark, M. Wun-Fogle, Thomas A. Lograsso May 2002

Temperature And Stress Dependencies Of The Magnetic And Magnetostrictive Properties Of Fe0.81ga0.19, R. A. Kellogg, Alison B. Flatau, A. E. Clark, M. Wun-Fogle, Thomas A. Lograsso

Ames Laboratory Conference Papers, Posters, and Presentations

It was recently reported that the addition of nonmagnetic Ga increased the saturation magnetostriction (λ100) of Fe over tenfold while leaving the rhombohedral magnetostriction (λ111) almost unchanged. To determine the relationship between the magnetostriction and the magnetization we measured the temperature and stress dependence of both the magnetostriction and magnetization from −21 °C to +80 °C under compressive stresses ranging from 14.4 MPa to 87.1 MPa. For this study a single crystal rod of Fe0.81Ga0.19 was quenched from 800 °C into water to insure a nearly random distribution of Ga atoms ...


Magnetothermal Properties Of Single Crystal Dysprosium, A. S. Chernyshov, A. M. Tishin, Karl A. Gschneidner Jr., A. O. Pecharsky, Vitalij K. Pecharsky, Thomas A. Lograsso Jan 2002

Magnetothermal Properties Of Single Crystal Dysprosium, A. S. Chernyshov, A. M. Tishin, Karl A. Gschneidner Jr., A. O. Pecharsky, Vitalij K. Pecharsky, Thomas A. Lograsso

Ames Laboratory Conference Papers, Posters, and Presentations

The magnetocaloric properties (the adiabatic temperature change) of the high purity single crystalline dysprosium have been measured directly over the temperature range from 78 to 220 K in magnetic fields from 0 to 14 kOe applied along the easy magnetization direction (a-axis). These results are in good to excellent agreement, except for two regions (105 to 127 K, and 179 to 182 K), with the previous magnetocaloric effect data reported on lower purity dysprosium samples. The magnetic phase diagram of Dy has been refined based on the results of these measurements and two new high magnetic field phases have ...