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| 7. |
- Jonsson, P, et al.
(författare)
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Spin-glass-like transition in a highly concentrated Fe-C nanoparticle system
- 2001
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Ingår i: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS. - : ELSEVIER SCIENCE BV. - 0304-8853. ; 226, s. 1315-1316
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Tidskriftsartikel (refereegranskat)abstract
- A highly concentrated (17 vol%)Fe-C nano particle system, with a narrow size distribution d = 5.4 +/- 0.4 nm, has been investigated using magnetic AC susceptibility measurements covering a wide range of frequencies (17-170 Hz). A dynamic scaling analysis
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| 8. |
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| 9. |
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| 10. |
- MAGNUSSON, J, et al.
(författare)
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FLUX PINNING IN YBA2CU3O7 THIN-FILMS GROWN BY DC MAGNETRON SPUTTERING
- 1992
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Ingår i: Cryogenics (Guildford). - : Elsevier BV. - 0011-2275 .- 1879-2235. ; 32, s. 1084-1088
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of YBa2Cu3O7 (YBCO) were deposited on single crystalline LaAlO3 substrates using d.c. magnetron sputtering. The quality of the films has been assessed by X-ray diffraction; YBa2Cu3O7 grows epitaxially with the c-axis parallel to the substrate normal. For some choices of the deposition parameters in the sputtering process, it was found that secondary phases were precipitated in the films. By a deliberate choice of deposition parameters, semi-coherently grown Y2O3 (yttria) inclusions could be obtained. They had square platelet or cubical shapes with sizes from 5 - 20 nm and thickness approximately 10 nm. The superconducting properties of the YBa2Cu3O7 films were investigated using SQUID magnetometry. Magnetization measurements on films with different densities of semicoherent Y2O3 inclusions indicate an enhanced flux pinning capability with increasing inclusion density.
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| 11. |
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| 12. |
- NISKANEN, K, et al.
(författare)
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ANGULAR DEPENDENT MAGNETIC-PROPERTIES OF SINGLE-CRYSTAL BI-SR-CA-CU-O
- 1991
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Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 185, s. 2207-2208
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Tidskriftsartikel (refereegranskat)abstract
- The field, time and temperature dependence of the longitudinal component of the magnetization of a single crystal of BiSrCaCuO has been investigated by SQUID-magnetometry as a function of the tilt angle between the crystallographic c-axis and the applied magnetic field. We here discuss the results on the field and angular dependence of the magnetic response in zero field cooled magnetization experiments at low fields.
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| 13. |
- NISKANEN, K, et al.
(författare)
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ANISOTROPY IN SINGLE CRYSTALLINE BISRCACUO
- 1992
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Ingår i: Superconductors Science and Technology. - 0953-2048 .- 1361-6668. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- The longitudinal component of the magnetization of a single crystal of Bi2.2Sr1.7CaCu2O8 has been investigated by SQUID-magnetometry when the magnetic field is applied at different angles 0-degrees-90-degrees with respect to the crystallographic c-axis. The anisotropy of the system, deduced from the magnetization and relaxation rate data, indicates a mass anisotropy m(c)/m(ab) of order 20, a strikingly low value compared to what has been found from torque and magnetoresistance measurements m(c)/m(ab) almost-equal-to 3000.
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| 14. |
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| 15. |
- NISKANEN, K, et al.
(författare)
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NONLOGARITHMIC MAGNETIC-RELAXATION IN BI-SR-CA-CU-O SINGLE-CRYSTALS
- 1991
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Ingår i: Superconductors Science and Technology. - 0953-2048 .- 1361-6668. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- The time dependence of the low field susceptibility of a Bi2.2Sr1.7CaCu2O8 single crystal has been investigated in the field range 0.1-300 gauss and at temperatures 0.25 less-than-or-equal-to T/T(c) less-than-or-equal-to 0.9. The relaxation of the magnetization is found to change from a logarithmic to a non-logarithmic form as the applied field is increased, implying that a conventional flux creep model cannot sufficiently describe the behaviour.
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| 20. |
- NORLING, P, et al.
(författare)
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MAGNETIC-RELAXATION OF INTERGRANULAR CRITICAL-STATE IN SINTERED YBA2CU3O7-DELTA
- 1994
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Ingår i: Physica. C, Superconductivity. - : Elsevier BV. - 0921-4534 .- 1873-2143. ; 221, s. 169-176
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Tidskriftsartikel (refereegranskat)abstract
- The relaxation of the zero-field-cooled magnetisation of three sintered samples of YBa2Cu3O7-delta has been measured at low fields. Special attention was paid to the low-field regime where the motion of intergranular vortices is dominating the decay of the magnetisation. From the measured data the apparent activation energy for flux jumps, U0, was calculated. The extracted values fall in the range 0.6-2 eV, considerably higher than what has been found for the intragranular flux creep but in the same range as reported by others for intergranular creep. The samples showed somewhat different behaviours and the sample with the most homogeneous morphology had the lowest value of U0. This can be explained within theories for pinning in granular superconductors.
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| 23. |
- SANDLUND, L, et al.
(författare)
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DYNAMICS OF CU-MN SPIN-GLASS FILMS
- 1989
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 40, s. 869-872
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Tidskriftsartikel (refereegranskat)
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| 24. |
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| 25. |
- SVEDLINDH, P, et al.
(författare)
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ANTI-MEISSNER EFFECT IN THE BISRCACUO-SYSTEM
- 1989
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Ingår i: Physica. C, Superconductivity. - : Elsevier BV. - 0921-4534 .- 1873-2143. ; 162, s. 1365-1366
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Tidskriftsartikel (refereegranskat)
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| 26. |
- SVEDLINDH, P, et al.
(författare)
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MAGNETIC-RELAXATION IN AN ISOTROPIC EXTREME TYPE-II SUPERCONDUCTOR
- 1991
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 43, s. 2735-2741
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Tidskriftsartikel (refereegranskat)abstract
- The time dependence of the zero-field-cooled and thermoremanent magnetization of the isotropic extreme type-II superconductor PbMo6S8 has been measured at temperatures 0.7 less-than-or-equal-to T/T(c) less-than-or-equal-to 0.95 and for fields 1 less-than-or-equal-to H less-than-or-equal-to 300 G. The results show that the time dependence of the decay can be divided into three different field regimes: (1) A low-field regime with a closely logarithmic decay and a well-established critical state. The relaxation rate [partial M/partial ln(t)] increases as H-5 for the zero-field-cooled magnetization and as H-2.4 for the thermoremanent magnetization. The reduction in magnetization over 5 decades in time (0.3-3 X 10(4) s) is, at most, a few percent. (2) A crossover-field regime with a change from a logarithmic to a nonlogarithmic decay. (3) A high-field regime where the time dependence of the decay is well described by the expression delta-M approximately [ln(t/tau-0)]-alpha. The reduction in magnetization in the crossover- and high-field regimes is as large as 25-30% in the measured time interval. The results in the high-field regime are interpreted within the theory of collective flux creep. Comparisons are made with the magnetic relaxation found in anisotropic high-T(c) superconductors.
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| 27. |
- SVEDLINDH, P, et al.
(författare)
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NONLOGARITHMIC MAGNETIC-RELAXATION IN BI2.2SR1.7CACU2O8 SINGLE-CRYSTALS - EVIDENCE FOR COLLECTIVE FLUX PINNING
- 1991
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Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 176, s. 336-346
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Tidskriftsartikel (refereegranskat)abstract
- High precision magnetic relaxation measurements have been performed on BiSrCaCuO single crystals with the field H applied parallel to the c-axis. At temperatures T/T(c) > 0.5, the data exhibit two different field regimes. One for H < H* (H* corresponds to the field where full flux penetration of the sample is achieved) where the ZFC and RM magnetization relaxes logarithmically with time in agreement with the conventional flux creep model; a second one for H > H* where the relaxation follows a [ln(t/t0)]-alpha dependence. This relaxation law is predicted in the collective flux creep theory for J << J(c) as well as in the vortex-glass model. In the temperature range 0.25 < T/T(c) < 0.4, there is a change in character of the measured decay of the magnetization. This change in character is interpreted to arise from thermal fluctuations of the flux-line lattice giving rise to a considerable reduction in the pinning strength above the depinning temperature.
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| 31. |
- Andersson, JO, et al.
(författare)
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Monte Carlo studies of the dynamics of an interacting monodispersive magnetic-particle system
- 1997
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMER INST PHYSICS. - 0163-1829. ; 56:21, s. 13983-13988
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the dipole-dipole interaction on the dynamics of monodispersive ensembles of magnetic nanoparticles have been studied by Monte Carlo simulations. An increased interaction strength drives the system from a state with only individual partic
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| 35. |
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| 36. |
- Bexell, Ulf, et al.
(författare)
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ToF-SIMS depth profiling of (Ga,Mn)As capped with amorphous arsenic : effects of annealing time
- 2006
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 252:19, s. 7252-7254
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Tidskriftsartikel (refereegranskat)abstract
- The influence of annealing time on an amorphous As cap layer and the depth distribution of Mn atoms have been investigated. The results show that a 1600 Å thick As cap layer is completely desorbed after 3 h of annealing time. The depth distributions of Mn indicate that interstitial Mn atoms have diffused to the outer surface and being passivated. The thickness of the Mn passivation layer was around 90 Å.
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| 37. |
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| 39. |
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| 40. |
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| 41. |
- Garcia-Palacios, JL, et al.
(författare)
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Nonlinear susceptibility of superparamagnets with a general anisotropy energy
- 2000
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Ingår i: PHYSICAL REVIEW B. - : AMERICAN PHYSICAL SOC. - 1098-0121. ; 61:10, s. 6726-6733
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium nonlinear response of noninteracting superparamagnets with a general single-spin anisotropy is investigated. Generalizing the results obtained for the simplest uniaxial anisotropy [Garcia-Palacios and Lazaro, Phys. Rev. B 55, 1006 (1997)],
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| 42. |
- Ginnarsson, K., et al.
(författare)
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Equilibrium and nonequilibrium magnetic behaviour of a reentrant Ising spin glass.
- 1992
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 104-107:3, s. 1607-1608
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Tidskriftsartikel (refereegranskat)abstract
- The reentrant Ising spin glass Fe0.62Mn0.38TiO3 has been investigated using SQUID magnetometry. The system is antiferromagnetic below TN(H = 0) = 33 K, and enters a mixed antiferromagnetic/spin glass phase below Tg(H = 0) = 25.8 K. Within the concept of a recent mean field model, a ratio TN(0)/Tg(0) close to unity indicates both intra- and interlayer frustration. The existence of an overlap length, lΔT, below which equilibrium spin correlations at temperatures T and T + ΔT are indistinguishable has been verified by magnetic relaxation experiments on this spin glass system
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| 45. |
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| 46. |
- Gunnarsson, K, et al.
(författare)
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Programmable motion and separation of single magnetic particles on patterned magnetic surfaces
- 2005
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 17:14, s. 1730-1734
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Tidskriftsartikel (refereegranskat)abstract
- Motion of single micrometer-sized magnetic particles on patterned magnetic surfaces is controlled by a rotating magnetic field (see Figure and cover). Patterns of thin-film magnetic elements are tailored to form transport lines. Individual particles are separated by adding junctions to the transport lines. The method can improve existing applications in biotechnology and generate new ones in life sciences.
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| 47. |
- GUNNARSSON, K, et al.
(författare)
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STATIC SCALING IN A SHORT-RANGE ISING SPIN-GLASS
- 1991
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 43, s. 8199-8203
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Tidskriftsartikel (refereegranskat)abstract
- The nonlinear ac susceptibility chi’-nl of the short-range Ising spin glass Fe0.5Mn0.5TiO3 has been measured using a superconducting-quantum-interference-device magnetometer. The spin-glass temperature, T(g), and the critical exponent gamma were estimated from the temperature dependence of the quadratic field term of chi’nl, yielding T(g) = 20.70 and gamma = 4.0. Static-scaling analyses, using different scaling equations, gave similar results. Using gamma and results from previous dynamic-scaling analyses, a number of critical exponents have been obtained through different scaling relations, e.g., delta = 8.4 and nu = 1.7. The results support the existence of a finite-temperature phase transition in a three-dimensional Ising spin glass.
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| 48. |
- Johnson, R. D., et al.
(författare)
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Temperature-induced phase transition from cycloidal to collinear antiferromagnetism in multiferroic Bi0.9Sm0.1FeO3 driven by f-d induced magnetic anisotropy
- 2017
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9969 .- 2469-9950. ; 95:5
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Tidskriftsartikel (refereegranskat)abstract
- In multiferroic BiFeO3 a cycloidal antiferromagnetic structure is coupled to a large electric polarization at room temperature, giving rise to magnetoelectric functionality that may be exploited in novel multiferroic-based devices. In this paper, we demonstrate that substituting samarium for 10% of the bismuth ions increases the periodicity of the room-temperature cycloid, and upon cooling to below similar to 15 K the magnetic structure tends towards a simple G-type antiferromagnet, which is fully established at 1.5 K. We show that this transition results from f-d exchange coupling, which induces a local anisotropy on the iron magnetic moments that destroys the cycloidal order-a result of general significance regarding the stability of noncollinear magnetic structures in the presence of multiple magnetic sublattices.
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| 49. |
- Jonsson, P, et al.
(författare)
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Nonlinear dynamic susceptibilities of interacting and noninteracting magnetic nanoparticles
- 2000
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Ingår i: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS. - : ELSEVIER SCIENCE BV. - 0304-8853. ; 222:1-2, s. 219-226
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Tidskriftsartikel (refereegranskat)abstract
- The linear and cubic dynamic susceptibilities of solid dispersions of nanosized maghemite gamma -Fe2O3 particles have been measured for three samples with a volume concentration of magnetic particles ranging from 0.3% to 17%, in order to study the effect
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| 50. |
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