| 1. |
- BAJOREK, A, et al.
(författare)
-
ON EXCHANGE MECHANISM IN HG1-XMNXS
- 1994
-
Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853 .- 1873-4766. ; 131, s. 363-368
-
Tidskriftsartikel (refereegranskat)abstract
- The magnetic susceptibility of Hg0.95Mn0.05S and Hg0.90Mn0.10S was measured by the SQUID technique. The experimental data were compared with the extended nearest neighbour pair approximation (ENNPA) calculation. The long range exchange interaction J = J(NN)R(-n), with the exponent n = 4, was found for both samples. The nearest neighbour exchange integral J(NN) was found to be around two times smaller than the effective exchange integral J(eff). The small value of the exponent n, which is a characteristic of the narrow gap semimagnetic semiconductors (SMSC’s), as well as the small J(NN)/J(eff) ratio, show the importance of a long-range exchange mechanism.
|
|
| 2. |
- Ginnarsson, K., et al.
(författare)
-
Equilibrium and nonequilibrium magnetic behaviour of a reentrant Ising spin glass.
- 1992
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 104-107:3, s. 1607-1608
-
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
|
|
| 3. |
- GRANBERG, P, et al.
(författare)
-
NONEQUILIBRIUM RELAXATION IN A CU(MN) SPIN-GLASS
- 1990
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 92, s. 228-232
-
Tidskriftsartikel (refereegranskat)abstract
- The zero-field dynamics of a Cu(10 at% Mn) spin glass system has been investigated by means of zero-field-cooled magnetization measurements. By subjecting the sample to specific temperature variations just before the field application, new information about the nature of the spin glass phase is obtained. The results are in accord with some predictions from domain theories on the behaviour of the magnetic relaxation in spin glasses. Specifically, the experimental results support the prediction that the spin glass dynamics is governed by an interplay between a growing domain size and the overlap length.
|
|
| 4. |
- Hanson, Maj, et al.
(författare)
-
Interaction effects in the dynamic response of magnetic liquids
- 1991
-
Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853 .- 1873-4766. ; 101, s. 45-46
-
Tidskriftsartikel (refereegranskat)abstract
- The magnetic susceptibility of magnetic liquids has been measured for frequencies up to 70 MHz. The imaginary part of the susceptibility exhibits a maximum around 10 MHz. This feature is interpreted as due to single-particle Néel relaxation, where particle interactions cause a slight concentration dependence in the position of the maximum.
|
|
| 5. |
- Johansson, Christer, et al.
(författare)
-
The magnetization of magnetic liquids containing amorphous Fe1-xCx particles
- 1993
-
Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853 .- 1873-4766. ; 122, s. 125-128
-
Tidskriftsartikel (refereegranskat)abstract
- The magnetization of amorphous Fe1-xCx particles in decalin was measured in magnetic fields up to 12 T at temperatures between 10 and 250 K. For particles with a diameter of 3.2 nm, the zero field cooled magnetization has a maximum at 20 K. This is interpreted as a blocking of the superparamagnetic relaxation of single particles.
|
|
| 6. |
- MATTSSON, J, et al.
(författare)
-
AGING IN A 2-DIMENSIONAL CUMN SPIN-GLASS
- 1992
-
Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853 .- 1873-4766. ; 104, s. 1623-1624
-
Tidskriftsartikel (refereegranskat)abstract
- Utilizing zero-field cooled magnetization measurements the nonequilibrium dynamics in a 2D spin glass film is investigated. The experiments show that aging is an inherent property of 2D spin glass systems with qualitatively similar features as in 3D systems.
|
|
| 7. |
- MATTSSON, J, et al.
(författare)
-
DETERMINATION OF THE CRITICAL EXPONENT-BETA FROM MEASUREMENTS OF A WEAK SPONTANEOUS MAGNETIZATION IN THE 3D ISING ANTIFERROMAGNET FEF2
- 1994
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 136
-
Tidskriftsartikel (refereegranskat)abstract
- The critical exponent for the order parameter, beta, has been determined from the temperature dependence of a weak spontaneous magnetisation that appears below the Neel temperature in the prototypical 3d Ising antiferromagnet FeF2. The derived value of beta = 0.325 +/- 0.002 agrees with the theoretically calculated value for beta of a 3d Ising system. The very occurrence of a spontaneous magnetisation in pure FeF2 is assumed to be of piezomagnetic origin.
|
|
| 8. |
- MATTSSON, J, et al.
(författare)
-
MULTILAYERED SPIN-GLASS FILMS - SENSITIVE PROBES OF RKKY
- 1992
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 104, s. 1619-1620
-
Tidskriftsartikel (refereegranskat)abstract
- A new method that uses superstructures of Cu(Mn) spin glass films separated by metallic interlayers to probe the decay with thickness of the RKKY interaction within the interlayers is discussed.
|
|
| 9. |
- MATTSSON, J, et al.
(författare)
-
NONLINEAR SUSCEPTIBILITY OF 2D SPIN-GLASS FILMS
- 1992
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 104, s. 1621-1622
-
Tidskriftsartikel (refereegranskat)abstract
- A careful study of the nonlinear susceptibility of multilayered two-dimensional Cu(14 at% Mn) spin glass layers separated by thick interlayers of Cu is reported. The experiments were performed in SQUID magnetometers using an ac susceptibility technique in the field range 0-0.5 kG and dc magnetization measurements in the field range 0-10 kG. The static 2D critical exponents have been determined from scaling analyses.
|
|
| 10. |
- SPASOJEVIC, V, et al.
(författare)
-
MAGNETIC-SUSCEPTIBILITY OF THE SEMIMAGNETIC SEMICONDUCTOR HG1-XMNXS
- 1993
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 118, s. 152-158
-
Tidskriftsartikel (refereegranskat)abstract
- The magnetic susceptibility of Hg1-xMnxS (x = 0.05, 0.10, 0.20, 0.30) has been measured in a SQUID magnetometer (T = 2-250 K) in a magnetic field of 9 kG. The high-temperature susceptibility of Hg1-xMnxS was found to behave in accordance with the Curie-Weiss law. From chi(T) measurements, for the first time, the microscopic parameter J1/k(B) = -(6.3 +/- 0.1) K (effective exchange integral) has been obtained. A spin S = 2.48 +/- 0.09, close to its atomic value S = 5/2, was also found. Low-temperature susceptibility measurements show that the sample with the highest Mn-concentration (x = 0.30) exhibits a difference between field-cooled and zero-field-cooled susceptibility signalling a spin-glass phase transition at about 4 K. As Hg1-xMnxS is the last uninvestigated alloy from the A1-xIIMnxBVI group, a complete review of experimental values (J1/k(B)) is also given.
|
|
| 11. |
- SRIVASTAVA, BK, et al.
(författare)
-
REENTRANT SPIN-GLASS-LIKE BEHAVIOR OF (FE0.90CR0.05NI0.05)2P
- 1994
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 132, s. 124-130
-
Tidskriftsartikel (refereegranskat)abstract
- Di-iron phosphide with small substitutions of iron with Cr and Ni, (Fe0.90Cr0.05Ni0.05)2P, has been investigated by SQUID-magnetometry. The sample exhibits a first order ferromagnetic transition at T(c) almost-equal-to 180 K and a re-entrant spin glass transition at T(g) almost-equal-to 125 K. The ferromagnetic transition is severely smeared by weak applied magnetic fields. The re-entrant transition is evidenced from both dc-magnetisation and ac-susceptibility measurements. An aging phenomenon is observed at temperatures below T(g) and the freezing temperatures, T(f), and their corresponding relaxation times, tau scale according to conventional critical slowing down: tau/tau0 = ((T(f) - T(g))/T(g))-znu, with an exponent znu almost-equal-to 9, a value that is found also at ordinary paramagnetic to spin glass transitions.
|
|
| 12. |
- Andersson, J-O, et al.
(författare)
-
Aging behaviour in two- and three-dimensional ising spin glasses studied by Monte Carlo simulations.
- 1992
-
Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853. ; 104-107, s. 1609-1610
-
Tidskriftsartikel (refereegranskat)abstract
- The nonequilibrium character of the spin glass dynamics has been studied in Monte Carlo simulations of two- and three-dimensional short-range Ising spin glass systems. The spin system was quenched in zero field to a temperature T. After equilibrating for a waiting time tw a weak magnetic field was applied and the time dependence of the magnetization M(t) was studied. Our results show that the relaxation rate, S(t) = ∂M(t)/∂log t, exhibits a maximum at a time t ≈ tw, which is consistent with results from experiments. If the temperature is increased or decreased prior to the field application, the apparent age ta of the system, as defined by the maximum in relaxation rate, is changed. The results are qualitatively in agreement with experiments as well as with theoretical models for the nonequilibrium spin glass dynamics
|
|
