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| 2. |
- Cedervall, Johan, et al.
(författare)
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Low temperature magneto-structural transitions in Mn3Ni20P6
- 2016
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Ingår i: Journal of Solid State Chemistry. - : Academic Press Inc.. - 0022-4596 .- 1095-726X. ; 237, s. 343-348
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Tidskriftsartikel (refereegranskat)abstract
- X-ray and neutron powder diffraction has been used to determine the crystal and magnetic structure of Mn3Ni20P6. The crystal structure can be described as cubic with space group Fm3¯m (225) without any nuclear phase transformation within studied temperature interval from room temperature down to 4 K. The magnetic structure of Mn3Ni20P6 is complex with two independent magnetic positions for the Mn atoms and the compound passes three successive magnetic phase transitions during cooling. At 30 K the spins of the Mn atoms on the Wyckoff 4a site (Mn1) order to form a primitive cubic antiferromagnetic structure with propagation vector k=(0 0 1). Between 29 and 26 K the Mn atoms on the Wyckoff 8c site (Mn2) order independently on already ordered Mn1 magnetic structure forming a commensurate antiferromagnetic structure with propagation vector k=(0 0 12) and below 26 K, both Mn positions order to form an incommensurate helical structure with propagation vector k=(0 0 ~0.45). Magnetization vs. temperature curve of Mn3Ni20P6 shows a steep increase indicating some magnetic ordering below 230 K and a sharp field dependent anomaly in a narrow temperature range around 30 K.
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| 3. |
- Chai, Guocai, et al.
(författare)
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Mechanisms of Hydrogen Induced Stress Crack Initiation and Propagation in Super Duplex Stainless Steels
- 2009
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Ingår i: STEEL RESEARCH INTERNATIONAL. - 1611-3683. ; 80:7, s. 482-487
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Tidskriftsartikel (refereegranskat)abstract
- Austenitic and ferritic duplex stainless steels, DSS, have recently suffered from hydrogen stress induced cracking, HISC, in subsea components with a cathodic protection. This paper provides discussions on possible HISC mechanisms. HISC initiation can occur at the ferritic grain boundaries and phase boundaries at a stress lower than the yield strength, but dominantly at phase boundaries at a stress higher than the yield strength. EBSD analysis shows that HISC in DSS results from the interaction between the dynamic plasticity by creep and hydrogen diffusion. A model on the formation of microstresses in these two phases under creep conditions is proposed, which explains why HISC occurs mainly in the ferritic phase. Discontinuous two-dimensional HISC paths were observed. The austenitic phase acts as obstacles for crack propagation. The fracture covers "valleys" and "peaks" with the cleavage ferrite and the austenite with microfacets or striations due to the hydrogen-enhanced localized-plasticity.
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| 4. |
- Eriksson, Therese, et al.
(författare)
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Complex magnetic properties of Mn3Ni20P6 and ferromagnetic structure of the new isostructural compound Mn3Pd20P6
- 2007
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 308:2, s. 203-209
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Tidskriftsartikel (refereegranskat)abstract
- A new compound, Mn3Pd20P6, has been synthesized and the crystal and magnetic structures have been determined by neutron powder diffraction. The crystal structure is cubic, with a = 11.9563(2) angstrom, space group Fm (3) over barm, and is isostructural to Mn3Ni20P6, a ternary ordering variant of the Cr23C6-type structure. The magnetic properties of Mn3Pd20P6 and Mn3Ni20P6 were studied by magnetization measurements. For Mn3Pd20P6 a transition, suggested to be of first order, to a ferromagnetic structure takes place at 110 K, whereas the saturation magnetization shows unusual temperature dependence. Magnetization vs. field loops show very weak coercivity, and the magnitude of the saturation magnetization agrees well with parallel Mn magnetic moments on two different sublattices of 4.24(8) mu(B), and 2.88(8) mu(B), respectively, found by neutron powder diffraction at 10 K. Magnetization vs. temperature measurements for Mn3Ni20P6 do not show a well-defined transition temperature, but show signatures of magnetic order with small excess magnetic moments aligned by the applied field below about 240 K. Further, signatures of a spin reorientation process at around 30 K are noted.
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| 5. |
- Felton, Solveig, et al.
(författare)
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Magnetic properties of TlCu2–xFexSe2 crystals
- 2005
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 97:10, s. 10B311-
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of two compositions of random solutions in the TlCu2–xFexSe2 system with x=0.2 and 0.45 have been investigated by superconducting quantum interference device magnetometry. The crystal structure is of a layer type and ordering due to the iron atoms occurs at low temperatures, with Tc=85 K for x=0.2 and Tc=130 K for x=0.45. The samples were highly textured crystals and the magnetic moments of both compositions were found to align along the c axis of the structure. The saturation moments were found to be 1.5µB/Fe for x=0.2 and 0.66µB/Fe for x=0.45.
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| 6. |
- Kamali-Moghaddam, Saeed, et al.
(författare)
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TlCu1.73Fe0.27Se2 studied by means of Mössbauer spectroscopy and SQUID magnetometry
- 2006
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 18:31, s. 7373-7382
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Tidskriftsartikel (refereegranskat)abstract
- TlCu2-xFexSe2 is a p-type metal for x < 0.5 which crystallizes in a body-centred tetragonal structure. The metal atoms are situated in ab-planes, similar to 7 angstrom apart, while the metal - metal distance within the plane is similar to 2.75 angstrom. Due to the large difference in cation distances, the solid solutions show magnetic properties of mainly two-dimensional character. The SQUID measurements performed for x = 0.27 give the c-axis as the easy axis of magnetization, but also show clear hysteresis effects at 10 K, indicating a partly ferromagnetic coupling. The magnetic ordering temperature T-c is 55( 5) K as found from both SQUID and Mossbauer spectra. At T << Tc the magnetic hyperfine fields are distributed with a maximum at about 30 T, which are compared to the measured magnetic moment per iron atom, which is 0.97 mu(B)/Fe as found from SQUID measurements. The experimental results are compared to results using other methods on isostructural Tl selenides.
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| 7. |
- Kamali, Saeed, et al.
(författare)
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Magnetic Properties of TlCo2Se2 Studied by Mössbauer Spectroscopy
- 2004
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Ingår i: Hyperfine Interactions. - 0304-3843 .- 1572-9540. ; 156/157:1-4, s. 315-319
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Tidskriftsartikel (refereegranskat)abstract
- The quasi two-dimensional antiferromagnetic compound TlCo2Se2 has been studied by 57Fe Mössbauer spectroscopy. Small single crystals have been made with 2% Fe doping. The Mössbauer spectrum, developed below the Néel temperature of 85 K, reveals a distribution of magnetic hyperfine fields (MHF). The fit is reasonably good if we suppose a connection between the values and mutual orientation of the EFG and MHF. That allows us to suggest the existence of a modulation in the helical magnetic structure, discovered earlier by neutron diffraction.
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| 8. |
- Lizárraga, Raquel, et al.
(författare)
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On the magnetic structure of TlCo2Se2
- 2004
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 272:557, s. 272-276
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of TlCo2Se2 have been investigated by means of first principles calculations. The magnetism of this compound is dominated by the contribution from the Co atoms, which form layers with a square coordination. The magnetic moments are arranged ferromagnetically within the ab-plane and in a non-collinear manner between consecutive planes.
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| 9. |
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| 10. |
- Ronneteg, Sabina, et al.
(författare)
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A neutron powder diffraction study of the helimagnetic structure of TlCo2Se2−xSx
- 2010
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 322:6, s. 681-685
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Tidskriftsartikel (refereegranskat)abstract
- The magneti clayer structure of TlCo2Se2-xSx has been thoroughly re-investigated with neutron powder diffraction. The cobalt magnetic moments are ferromagnetically arranged with in the layers, but the interlayer coupling differs profoundly with varying composition (x): the spins in TlCo2Se2 form a helix along the c-axis with a turning-angle of similar to 119 degrees at 1.4 K. This kind of helical structure prevails for 0 <= x <= 1.5 with a gradual decrease of the angle with increasing sulphur content, down to 34 degrees, showing an almost linear relationship with the interlayer distance of Co-Co. For x >= 1.75 the interlayer couplingchanges to ferromagnetic. Unexpectedly, two helices were found to coexist at x = 0.5 and x = 1.0. The interaction between adjacent cobalt layers is there characterized by an incommensurate angle (106 degrees, resp., 73 degrees) together with a commensurate angle of 90 degrees. The magnetic structures have been refined as two magnetic phases, each having a characteristic wave vector. A tentative model where the symmetry of the structure and the interlayer distance compete is considered for explaining the simultaneous occurrence of the two kinds of diffraction profile satellites.
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