Superparamagnetic behaviour of antiferromagnetic DyPO4 nanoparticles

We report on the low-temperature magnetic ac-susceptibility of antiferromagnetic DyPO4 nanoparticles with a very high surface to volume ratio. The results are interpreted in terms of superparamagnetic relaxation of the Neel vector arising from a relatively large number approx 0.2 Na of uncompensated spins probably existing on the surface of the nanoparticles. The activation energy of the relaxation process is found to be Ea / kB = (2.6+-0.1) K within a model taking into account the magnetic interaction between nanoparticles.Comment: 3 pages, 1 figure, Espcrc2, ICM0

Phase diagrams of weakly anisotropic Heisenberg antiferromagnets: II. Quasi 2-dimensional systems

Quantum Matter and Optic

Spin-Peierls transition in a Cu2+ linear chain

Metals in Catalysis, Biomimetics & Inorganic Material

Quantum tunnelling of magnetization in Mn12-ac studied by 55Mn NMR

We present an ultra-low temperature study (down to T = 20 mK) of the nuclear spin-lattice relaxation (SLR) in the 55Mn nuclei of the molecular magnet Mn12-ac. The nuclear spins act as local probes for the electronic spin fluctuations, due to thermal excitations and to tunnelling events. In the quantum regime (below T = 0.75 K), the nuclear SLR becomes temperature-independent and is driven by fluctuations of the cluster's electronic spin due to the quantum tunnelling of magnetization in the ground doublet. The quantitative analysis of the nuclear SLR shows that the presence of fast-tunnelling molecules, combined with nuclear intercluster spin diffusion, plays an important role in the relaxation process.Comment: RevTex, 5 pages, 3 eps figures; presented at the Internation Conference on Molecular Magnets (Valencia, 5 - 10 Oct. 2002); to be published in Polyhedro

High-field (40 T) magnetization studies of linear Heisenberg chains with alternating exchange

Metals in Catalysis, Biomimetics & Inorganic Material

Non-linear excitations in Ising-type magnetic chain systems I: Mossbauer relaxation studies of antiferromagnets in zero and applied field

Quantum Matter and Optic

Nuclear spin dynamics in the quantum regime of a single-molecule magnet

Quantum Matter and Optic

Field-dependent Mossbauer relaxation study of domain walls in the quasi 1-d antiferromagnet RbFeCl3.2H2O

Quantum Matter and Optic

Solid state magic angle spinning13C and31P NMR of organic ligand stabilized high nuclearity metal clusters: 13C and31P MAS on metal cluster compounds

C-13 and P-31 Solid state NMR measurements on the organic ligands in ligated Au55, Ni8, Pt309, Cu36 and Cu70 clusters are reported. The ligands behave like diamagnetic organic molecules, giving rise to relatively narrow lines with excellent cross-polarization efficiency. The resonance lines of the nuclei directly bound to the metal core are systematically broadened in the conducting compounds. No pronounced Knight shifts or evidence of metallic-like relaxation were observed. These results support a model for the electrical conduction involving tunneling between metal cores with the ligands playing the role of a tunneling barrier.Quantum Matter and OpticsSolid state NMR/Biophysical Organic Chemistr