Author
Thomas A. Lograsso
Other affiliations: Iowa State University, CBS Laboratories, United States Department of Energy
Bio: Thomas A. Lograsso is an academic researcher from Ames Laboratory. The author has contributed to research in topics: Magnetostriction & Magnetization. The author has an hindex of 47, co-authored 307 publications receiving 10137 citations. Previous affiliations of Thomas A. Lograsso include Iowa State University & CBS Laboratories.
Papers published on a yearly basis
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TL;DR: In this paper, a simple model accounts quantitatively for the dependence of strain on magnetic field and external stress using as input parameters only measured quantities, and the strain versus field curves exhibit appreciable hysteresis associated with the motion of the twin boundaries.
Abstract: Field-induced strains of 6% are reported in ferromagnetic Ni–Mn–Ga martensites at room temperature. The strains are the result of twin boundary motion driven largely by the Zeeman energy difference across the twin boundary. The strain measured parallel to the applied magnetic field is negative in the sample/field geometry used here. The strain saturates in fields of order 400 kA/m and is blocked by a compressive stress of order 2 MPa applied orthogonal to the magnetic field. The strain versus field curves exhibit appreciable hysteresis associated with the motion of the twin boundaries. A simple model accounts quantitatively for the dependence of strain on magnetic field and external stress using as input parameters only measured quantities.
1,035 citations
01 Sep 2000
TL;DR: The magnetic and magnetostrictive properties of Fe/sub 1-x/Ga/sub x/ and Fe sub 1x-y/Al/sub y/ (a+y < 0.3) single crystals were measured under compressive stresses up to 120 MPa and in magnetic fields up to 1 kOe as discussed by the authors.
Abstract: The magnetic and magnetostrictive properties of Fe/sub 1-x/Ga/sub x/ and Fe/sub 1-x-y/Ga/sub x/Al/sub y/ (a+y<0.3) single crystals were measured under compressive stresses up to 120 MPa and in magnetic fields up to 1 kOe. Values of /spl lambda//sub 100/ exceeding 200 ppm were observed in samples of Fe/sub 83/Ga/sub 17/ from 180 K to room temperature. Only a small monotonic decrease in magnetostriction with temperature was found. On the other hand, /spl lambda//sub 111/ maintained small negative values close to those of b.c.c. Fe. In all cases, no higher order magnetostrictive terms were detectable. With 15 to 20 atomic percent replacement of Fe by Ga, the magnetizations remain high (M, /spl cong/1.8 T) and the magnetic anisotropies reduced (K/sub 1//spl cong/10/sup 4/ J/m/sup 3/). Values of the 'stiff' (high magnetic field) Young's modulus, Bulk modulus, Poison's ratio, and elastic constant C/sub 11/-C/sub 12/ for Fe/sub 85/Ga/sub 15/ at room temperature are, respectively, 77 GPa, 111 GPa, 0.38, and 56 GPa.
628 citations
TL;DR: In this article, a single maximum in the magnetoelastic coupling |b1| of Fe with increasing amounts of nonmagnetic Ga, combined with a strongly temperature dependent elastic shear modulus (c11−c12) is interpreted as anomalous magnetostrictive behavior in Fe-Ga alloys.
Abstract: Extraordinary magnetostrictive behavior has been observed in Fe-Ga alloys with concentrations of Ga between 4% and 27%. λ100 exhibits two peaks as a function of Ga content. At room temperature, λ100 reaches a maximum of 265 ppm near 19% Ga and 235 ppm near 27% Ga. For compositions between 19% and 27%, λ100 drops sharply to a minimum near 24% Ga and exhibits an anomalous temperature dependence, decreasing by as much as a factor of 2 at low temperatures. This unusual magnetostrictive behavior is interpreted on the basis of a single maximum in the magnetoelastic coupling |b1| of Fe with increasing amounts of nonmagnetic Ga, combined with a strongly temperature dependent elastic shear modulus (c11−c12) which approaches zero near 27% Ga. λ111 is significantly smaller in magnitude than λ100 over this composition range, and has an abrupt change in sign from negative for low Ga concentrations to positive for a concentration of Ga near 21%.
503 citations
TL;DR: Although conventional wisdom calls for special conditions, such as non-stoichiometry, metastable disorder or doping to achieve some ductility in intermetallic compounds at room temperature, none of these is required in these unique B2 rare-earth compounds.
Abstract: Stoichiometric intermetallic compounds have always been touted for their attractive chemical, physical, electrical, magnetic and mechanical properties, but few practical uses have materialized because they are brittle at room temperature1,2,3,4. Here we report on a large family of fully ordered, stoichiometric binary rare-earth intermetallic compounds with high ductility at room temperature. Although conventional wisdom calls for special conditions, such as non-stoichiometry, metastable disorder or doping to achieve some ductility in intermetallic compounds at room temperature, none of these is required in these unique B2 rare-earth compounds. Ab initio calculations of YAg, YCu and NiAl crystal defect energies support the observed deformation modes of these intermetallics.
306 citations
TL;DR: The magnetostriction of b.c. Fe is increased over 10-fold at room temperature by the substitution of /spl sim/20% gallium for Fe as mentioned in this paper.
Abstract: The magnetostriction (/spl lambda//sub 100/) of b.c.c. Fe is increased over 10-fold at room temperature by the substitution of /spl sim/20% gallium for Fe. Fe/sub 1-x/Ga/sub x/ alloys with x between 0.19 and 0.214 that are quenched from 800/spl deg/C exhibit magnetostrictions /spl sim/25% higher than those furnace-cooled at 10/spl deg//min. We propose that this great increase of magnetostriction above that of Fe in Fe-Ga alloys is not due to conventional magnetoelastic effects but due to the substitutive presence of asymmetrically shaped clusters of the Ga atoms. As the concentration of solute atoms approaches 25%, the lattice becomes relaxed with formation of a more ordered structure and the magnetostriction decreases in value.
253 citations
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28 Jul 2005
TL;DR: PfPMP1）与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。
18,940 citations
TL;DR: In this article, a selfconsistent and logical account of key issues on Ti-Ni-based alloys from physical metallurgy viewpoint on an up-to-date basis is presented.
3,484 citations
TL;DR: In this article, a review of mostly recent activities can be found, with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972.
Abstract: Multiferroic magnetoelectric materials, which simultaneously exhibit ferroelectricity and ferromagnetism, have recently stimulated a sharply increasing number of research activities for their scientific interest and significant technological promise in the novel multifunctional devices. Natural multiferroic single-phase compounds are rare, and their magnetoelectric responses are either relatively weak or occurs at temperatures too low for practical applications. In contrast, multiferroic composites, which incorporate both ferroelectric and ferri-/ferromagnetic phases, typically yield giant magnetoelectric coupling response above room temperature, which makes them ready for technological applications. This review of mostly recent activities begins with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972. In such composites the magnetoelectric effect is generated as a product property of a magnetostrictive and a piezoelectric substance. A...
3,288 citations
01 Sep 1955
TL;DR: In this paper, the authors restrict their attention to the ferrites and a few other closely related materials, which are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present.
Abstract: In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.
2,659 citations