Field-induced Structural Transition Research Articles

Ferromagnetism in the austenitic and martensitic states ofNi−Mn−Inalloys

The magnetic and structural transformations in the Heusler-based system ${\mathrm{Ni}}_{0.50}{\mathrm{Mn}}_{0.50\ensuremath{-}x}{\mathrm{In}}_{x}$ are studied in the composition range $0.05\ensuremath{\leqslant}x\ensuremath{\leqslant}0.25$. While the cubic phase is preserved in the range $0.165\ensuremath{\leqslant}x\ensuremath{\leqslant}0.25$, we find the presence of martensitic transformations in alloys with $x\ensuremath{\leqslant}0.16$. In a critical composition range $0.15\ensuremath{\leqslant}x\ensuremath{\leqslant}0.16$, the magnetic coupling in both austenitic and martensitic states is ferromagnetic. Magnetic field-induced structural transitions are also found in the $x=0.16$ alloy, whereby the structural transition temperature shifts by $42\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ in a field of $50\phantom{\rule{0.3em}{0ex}}\mathrm{kOe}$.

Field-induced structural transition and quasistatic susceptibility of one-dimensional magnetic nanoparticle chains

Field-induced structural transition and quasistatic susceptibility of one-dimensional magnetic nanoparticle chains

Large Magnetic Entropy Change near Charge-Ordered Transition Temperature in Nd0.5Sr0.5MnO3

Large magnetic entropy change (7.5 J/kg·K) was discovered in Nd 0.5 Sr 0.5 MnO 3 under a low magnetic field of 10 kOe at charge-ordered state transition temperature (183 K). It exceeds the magnetic entropy change in Gd by a factor of 2.4 at phase transition temperature under same magnetic field. The physical mechanism is related to the field-induced first-order magnetic, electron and structural transition (from antiferromagnetic charge-ordered state to ferromagnetic charge-disordered state).

Magnetotransport properties and magnetostructural phenomenon in single crystals ofLa0.7(Ca1−ySry)0.3MnO3

The magnetotransport and magnetostructural properties of ${\mathrm{La}}_{0.7}({\mathrm{Ca}}_{1\ensuremath{-}y}{\mathrm{Sr}}_{y}{)}_{0.3}{\mathrm{MnO}}_{3}$ $(0l~yl~1)$ are studied. We investigate the variation in magnetoresistance (MR) with y and the field-induced structural transition at $y\ensuremath{\sim}0.5$ by using single crystals prepared by the floating-zone method. With the increase in y, the colossal MR behavior at $y\ensuremath{\sim}0$ is transformed to a rather canonical MR (a MR free from lattice effects) at $y=1.$ The coefficient C in the empirical relation that $\ensuremath{\rho}(M)/\ensuremath{\rho}(0)=\mathrm{exp}[\ensuremath{-}{C(M/M}_{s}{)}^{2}]$ (M and ${M}_{s}$ being the magnetization and its zero-temperature saturation value) shows a significant change with y, attainable for example, from 7.6 at $y=0.1$ to 2.3 at $y=0.7.$ As an example of the magnetoswitching of a crystal structure around room temperature, the structural-phase transition induced by an external magnetic field is investigated for crystals with $y\ensuremath{\sim}0.5.$ Structural-phase diagrams of the magnetic field vs temperature plane are given.

Simulation of field-induced structural formation and transition in electromagnetorheological suspensions.

A computer simulation method has been used to study the three-dimensional structural formation and transition of electromagnetorheological (EMR) suspensions under compatible electric and magnetic fields. When the fields are applied simultaneously and perpendicularly to each other, the particles rapidly arrange into single layer structures parallel to both fields. In each layer, there is a two-dimensional hexagonal lattice. The single layers then combine together to form thicker sheetlike structures. With the help of the thermal fluctuations, the thicker structures relax into three-dimensional close-packed structures, which may be face-centered cubic (fcc), hexagonal close-packed (hcp) lattices, or, more probably, the mixture of them, depending on the initial configurations and the thermal fluctuations. On the other hand, if the electric field is applied first to induce the body-centered tetragonal (bct) columns in the system, and then the magnetic field is applied in the perpendicular direction, the bct to fcc structure transition is observed in a very short time. Following that, the structure keeps on evolving due to the demagnetization effect and finally forms close-packed structures with fcc and hcp lattice character. The simulation results are in agreement with the theoretical and experimental results.

Field-induced structural transition in mesocrystallites

We have fabricated multiply-coated microspheres that exhibit appreciable electro-magneto-rheological responses. Under crossed electric and magnetic fields, the microspheres form columnar crystallites with an internal structure that transforms from body-centered tetragonal to face-centered cubic as the ratio between the magnetic and the electric fields exceeded a minimum value. The observed transition scenarios are in excellent agreement with calculations.

Magnetic-field-induced structural phase transition inGd5(Si1.8Ge2.2)

We present direct evidence that the giant magnetocaloric effect recently discovered in the ${\mathrm{Gd}}_{5}{(\mathrm{S}\mathrm{i}}_{1.8}{\mathrm{Ge}}_{2.2})$ alloy is associated with a field-induced first-order structural transition from a ${P112}_{1}/a$ monoclinic (paramagnetic) to a Pnma orthorhombic (ferromagnetic) structure. A large volume contraction of $\ensuremath{\Delta}V/V\ensuremath{\cong}0.4%$ takes place spontaneously at the transition temperature, ${T}_{C}\ensuremath{\cong}240\mathrm{K}.$ The reported structural transition can be induced reversibly by application of an external magnetic field, producing strong magnetoelastic effects.

Unusual Conductive Behavior of (BEDT-TTF)3Cl2 Hydrate Salts

Abstract The ion-radical salt (BEDT-TTF)3Cl2*5H2O has been prepared through electro-crystallization using halocarbons as a solvent in the presence of an aliquot of water. The crystal structure was characterized by a multi-layered structure consists of organic layers of a donor stack and inorganic layers of hydrated chloride ions. When the resistivity was measured, the salt showed a rectifying effect. This effect may be caused by the external field-induced structural transition of chloride ions coupled with the change of a hydration scheme.