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506 results on '"Oomi, G."'

2. Valence instability of cerium under pressure in the Kondo-like perovskite La$_{0.1}$Ce$_{0.4}$Sr$_{0.5}$MnO$_3$

Author

Eto, T., Sundaresan, A., Honda, F., and Oomi, G.

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science
Abstract

Effect of hydrostatic pressure and magnetic field on electrical resistance of the Kondo-like perovskite manganese oxide, La$_{0.1}$Ce$_{0.4}$Sr$_{0.5}$MnO$_3$ with a ferrimagnetic ground state, have been investigated up to 2.1 GPa and 9 T. In this compound, the Mn-moments undergo double exchange mediated ferromagnetic ordering at $T_{\rm C}$ $\sim$ 280 K and there is a resistance maximum, $T_{\rm max}$ at about 130 K which is correlated with an antiferromagnetic ordering of {\it cerium} with respect to the Mn-sublattice moments. Under pressure, the $T_{\rm max}$ shifts to lower temperature at a rate of d$T_{max}$/d$P$ = -162 K/GPa and disappears at a critical pressure $P_{\rm c}$ $\sim$ 0.9 GPa. Further, the coefficient, $m$ of $-logT$ term due to Kondo scattering decreases linearly with increase of pressure showing an inflection point in the vicinity of $P_{\rm c}$. These results suggest that {\it cerium} undergoes a transition from Ce$^{3+}$ state to Ce$^{4+}$/Ce$^{3+}$ mixed valence state under pressure. In contrast to pressure effect, the applied magnetic field shifts $T_{\rm max}$ to higher temperature presumably due to enhanced ferromagnetic Mn moments., Comment: to be published in Phys. Rev. B (rapid commun)

Published
2005
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3. Thermal expansion of CeRhSb under high pressure

Author

Ishii, T, Oomi, G, Uwatoko, Y, Thompson, JD, Madru, D, Shero, JL, and Fisk, Z

Subjects
CeRhSb, thermal expansion, high pressure, Condensed Matter Physics, Quantum Physics, Macromolecular and Materials Chemistry, General Physics
Abstract

The linear thermal expansion of polycrystalline CeRhSb has been measured in the temperature range 77 K < T < 300 K under hydrostatic pressure up to 2.3 GPa. It is found that the thermal expansion coefficient α(T) at ambient pressure shows a maximum around Tmax = 140 K and Tmax increases with increasing pressure having rate of ∂Tmax/∂P = + 38.5 K/GPa. This fact shows that the Kondo temperature TK is increased by applying pressure.

Published
1997

4. Effect of pressure on the electrical resistivity and magnetization of CeScGe

Author

Sarrao, JL, Mandrus, D, Fisk, Z, Thompson, JD, Uwatoko, Y, Ishii, T, Oomi, G, Takahashi, H, Mori, N, Nimori, S, and Kido, G

Subjects
Condensed Matter Physics, Quantum Physics, Macromolecular and Materials Chemistry, General Physics
Abstract

Measurement of the magnetization up to H = 30 T at 4.2 K, temperature dependence of magnetic susceptibility and effect of pressure on the electrical resistivity on CeScGe are presented. These results indicate that CeScGe is antiferromagnetic with TN = 46 K. The Néel temperature TN decreases with increasing pressure with the rate of dTN/dP= -0.56K/kbar.

Published
1997

5. Effect of pressure on the electrical resistivity and magnetization of CeScGe

Author

Uwatoko, Y, Ishii, T, Oomi, G, Takahashi, H, Mori, N, Nimori, S, Kido, G, Sarrao, JL, Mandrus, D, Fisk, Z, and Thompson, JD

Subjects
Condensed Matter Physics, Quantum Physics, Macromolecular and Materials Chemistry, General Physics
Abstract

Measurement of the magnetization up to H = 30 T at 4.2 K, temperature dependence of magnetic susceptibility and effect of pressure on the electrical resistivity on CeScGe are presented. These results indicate that CeScGe is antiferromagnetic with TN = 46 K. The Néel temperature TN decreases with increasing pressure with the rate of dTN/dP= -0.56K/kbar.

Published
1997

6. Electrical resistivity and effect of pressure on the thermal expansion of a single crystal of YbCu2Si2

Author

Uwatoko, Y, Oomi, G, Thompson, JD, Canfield, PC, and Fisk, Z

Subjects
Condensed Matter Physics, Quantum Physics, Macromolecular and Materials Chemistry, General Physics
Abstract

Electrical resistivity ρ(T) and thermal expansion Δl/l were measured for the intermediate valence compound (IVC) YbCu2Si2 and its counterpart LuCu2Si2 between 4.2 K and 300 K. It was found that the thermal expansion coefficient α(T) has a negative minimum around 31 K (=Tmin) at atmospheric pressure and Tmin decreases with increasing pressure at the rate δTmin/δT = -0.45 K/kbar. © 1993.

Published
1993

11. Pressure dependence of magnetoresistance for Fe/Cr multilayers

Author

Suenaga, K., Higashihara, S., Oomi, G., Saito, K., Mitani, S., and Takanashi, K.

Subjects
Magnetoresistance -- Analysis, Dielectric films -- Magnetic properties, Dielectric films -- Electric properties, Thin films -- Magnetic properties, Thin films -- Electric properties, Superlattices as materials -- Magnetic properties, Superlattices as materials -- Electric properties, Business, Electronics, Electronics and electrical industries
Abstract

The magnetoresistance (MR) in Fe/Cr magnetic multilayers (MML) has been measured under high pressure up to 2.5 GPa. It is found that the spin-dependent scattering plays an important role in the pressure dependence of MR ratio. In the present work, for [[Fe(20 [Angstrom])/Cr(10 [Angstrom])].sub.20] MML with antiferromagnetic (AF) state, the pressure coefficient of saturation field [H.sub.s] is (1/[H.sub.s])([partial derivative][H.sub.s]/P[partial derivative]) = 3.3 x [10.sup.-2] [GPa.sup.-1] between 0.1 and 2.5 GPa. We found that the (1/|J|)([partial derivative]|J|/[partial derivative]P) for AF-Fe/Cr MML with polycrystalline structure is opposite in sign to that with epitaxial one. For [Fe(20 [[Angstrom])/Cr(22 [Angstrom])].sub.20] MML with ferromagnetic (F) state, anisotropic magnetoresistance (AMR) decreases with increasing pressure. It is suggested that the anisotropy constant decreases with weakening spin-orbit interaction at high pressure. At high field, the AMR is easily suppressed by applying pressure while the giant magnetoresistance around [H.sub.s] increases slightly with increasing pressure for polycrystalline Fe/Cr MML. Index Terms--Giant magnetoresistance, multilayers, pressure effects, superlattices, thin films.

Published
2006

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