Search results for "magnetization"
showing 10 items of 550 documents
Ultrafast Optical Demagnetization manipulates Nanoscale Spin Structure in Domain Walls
2012
During ultrafast demagnetization of a magnetically ordered solid, angular momentum has to be transferred between the spins, electrons, and phonons in the system on femto- and picosecond timescales. Although the intrinsic spin-transfer mechanisms are intensely debated, additional extrinsic mechanisms arising due to nanoscale heterogeneity have only recently entered the discussion. Here we use femtosecond X-ray pulses from a free-electron laser to study thin film samples with magnetic domain patterns. We observe an infrared-pump-induced change of the spin structure within the domain walls on the sub-picosecond timescale. This domain-topography-dependent contribution connects the intrinsic dem…
Magnetization of3He spin filter cells
2007
A number of valved quartz glass 3He spin filter cells have been repeatedly exposed to various external magnetic fields in order to determine the influence of induced wall magnetization on the relaxation time in the cells. The procedures of magnetizing and degaussing of cells are described. A comparison of T1 measurements performed in the same cell by different methods attest the good reliability of the measurements as well as the time stability of T1 in Cs-coated quartz glass cells. No orientation dependence of the relaxation in fields of 8 G was observed. A strong dependence of T1 on the strengths of external magnetic fields, applied perpendicular to the direction of the guide field used d…
High-field nuclear spin relaxation in liquids and solids
1990
The authors generalise the standard theory of nuclear spin relaxation to situations in which the Markovian approximation is not applicable. Expressions for generalised frequency-dependent spin relaxation functions are presented. They show that under high-field conditions the relaxation of longitudinal magnetisation is exponential independent of the particular time dependence of the correlation functions.
Field-induced single ion magnet behaviour of discrete and one-dimensional complexes containing [bis(1-methylimidazol-2-yl)ketone]-cobalt(II) building…
2021
International audience; We describe herein the first examples of six-coordinate CoII single-ion magnets (SIMs) based on the β-diimine Mebik ligand [Mebik = bis(1-methylimidazol-2-yl)ketone]: two mononuclear [CoII(Rbik)2L2] complexes and one mixed-valence {CoIII2CoII}n chain of formulas [CoII(Mebik)(H2O)(dmso)(μ-NC)2CoIII2(μ-2,5-dpp)(CN)6]n·1.4nH2O (3) [L = NCS (1), NCSe (2) and 2,5-dpp = 2,5-bis(2-pyridyl)pyrazine (3)]. Two bidentate Mebik molecules plus two monodentate N-coordinated pseudohalide groups in cis positions build somewhat distorted octahedral surroundings around the high-spin cobalt(II) ions in 1 and 2. The diamagnetic [CoIII2(μ-2,5-dpp)(CN)8]2− metalloligand coordinates the pa…
Apoferritin-encapsulated Ni and Co superparamagnetic nanoparticles
2006
Ni and Co nanoparticles (average diameters 3 and 3.5 nm) have been prepared within the apoferritin cavity. The protein shell prevents bulk aggregation of the metal particles, rendering them water soluble. X-Ray diffraction, transmission electronic microscopy and magnetization measurements have been used for characterizing the nanoparticles. The magnetic study of both nanoparticles confirmed the expected superparamagnetic behavior.
A Mononuclear Uranium(IV) Single-Molecule Magnet with an Azobenzene Radical Ligand
2015
A tetravalent uranium compound with a radical azobenzene ligand, namely, [{(SiMe2NPh)3‐tacn}UIV(η2‐N2Ph2.)] (2), was obtained by one‐electron reduction of azobenzene by the trivalent uranium compound [UIII{(SiMe2NPh)3‐tacn}] (1). Compound 2 was characterized by single‐crystal X‐ray diffraction and 1H NMR, IR, and UV/Vis/NIR spectroscopy. The magnetic properties of 2 and precursor 1 were studied by static magnetization and ac susceptibility measurements, which for the former revealed single‐molecule magnet behaviour for the first time in a mononuclear UIV compound, whereas trivalent uranium compound 1 does not exhibit slow relaxation of the magnetization at low temperatures. A first approxim…
A polymeric two-dimensional mixed-metal network. Crystal structure and magnetic properties of {[P(Ph)4][MnCr(ox)3]}
1994
Abstract The mixed-metal ferromagnet {[P(Ph) 4 ][MnCr(ox) 3 ]} n , where Ph is phenyl and ox is oxalate, has been prepared and a two-dimensional network structure, extended by Mn(II)-ox-Cr(III) bridges, has been determined from single crystal X-ray data. Crystal data: space group R 3 c , a = b =18.783(3), c =57.283(24) A, α=β=90, γ=120°, Z =24 (C 30 H 20 O 12 PCrMn). The magnetic susceptibility data obey the Curie-Weiss law in the temperature range 260–20 K with a positive Weiss constant of 10.5 K. The temperature dependence of the molar magnetization exhibits a magnetic phase transition at T c =5.9 K. The structure is discussed in relation to the strategy for preparing molecular based ferr…
Slow Relaxation of the Magnetization in Anilato-Based Dy(III) 2D Lattices.
2021
The search for two- and three-dimensional materials with slow relaxation of the magnetization (single-ion magnets, SIM and single-molecule magnets, SMM) has become a very active area in recent years. Here we show how it is possible to prepare two-dimensional SIMs by combining Dy(III) with two different anilato-type ligands (dianions of the 3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone: C6O4X22−, with X = H and Cl) in dimethyl sulfoxide (dmso). The two compounds prepared, formulated as: [Dy2(C6O4H2)3(dmso)2(H2O)2]·2dmso·18H2O (1) and [Dy2(C6O4Cl2)3(dmso)4]·2dmso·2H2O (2) show distorted hexagonal honeycomb layers with the solvent molecules (dmso and H2O) located in the interlayer space and…
A hemispherical dynamo model : Implications for the Martian crustal magnetization
2014
Abstract Mars Global Surveyor measurements revealed that the Martian crust is strongly magnetized in the southern hemisphere while the northern hemisphere is virtually void of magnetization. Two possible reasons have been suggested for this dichotomy: a once more or less homogeneously magnetization may have been destroyed in the northern hemisphere by, for example, resurfacing or impacts. The alternative theory we further explore here assumes that the dynamo itself produced a hemispherical field ( Stanley et al., 2008 , Amit et al., 2011 ). We use numerical dynamo simulations to study under which conditions a spatial variation of the heat flux through the core–mantle boundary (CMB) may yiel…
Scattering in Strong Magnetic Fields
1985
Publisher Summary This chapter discusses collision processes in the presence of a strong magnetic field. The chapter deals with the potential scattering in a magnetic field arising in connection with the problem of Bremsstrahlung (“free–free transitions”) of an electron in the field. An expression for the photoionization cross section of a one-electron (hydrogenic) system in a magnetic field is also presented. A different approach is required to the problem of ion–atom collisions in a magnetic field because the collision energy E is generally much greater than hωc. Within the two-state model, not only did the magnetic field modify the bound-state wave functions, but, more importantly, it in…