Cu atoms deposited on a zero layer graphene grown on a SiC(0001) substrate, intercalate between the zero layer graphene and the SiC substrate after the thermal annealing above 600 °C, forming a Cu-intercalated single layer graphene. On the Cu-intercalated single layer graphene, a graphene lattice with superstructure due to moiré pattern is observed by scanning tunneling microscopy, and specific linear dispersion at the K¯ point as well as a characteristic peak in a C1s core level spectrum, which is originated from a free-standing graphene, is confirmed by photoemission spectroscopy. The Cu-intercalated single layer graphene is found to be n-doped.
We report the combined measurements of the dc susceptibility 0 , the ac susceptibility Ј, and the NMR relaxation rate T 1 −1 for the molecular-based heterometallic single-chain magnet ͓Mn͑saltmen͔͒ 2 ͓Ni͑pao͒ 2 ͑py͒ 2 ͔͑PF 6 ͒ 2 . At low temperatures, this system is well described by a one-dimensional array of effective spin S = 3 chains comprising the Mn III -Ni II -Mn III trimers and treated as the S = 3 Ising chain with the single-ion term ͑Blume-Capel model͒. Using the exact solution of the model and based on the picture that the random motion of the local domain walls dominates the low-temperature spin dynamics, we succeeded in reproducing the experimental results of the dc susceptibility 0 , the ac susceptibility Ј, and the 19 F-NMR relaxation rate T 1 −1 in a consistent manner.
The single-chain magnet ͑SCM͒ system ͓Mn 2 ͑saltmen͒ 2 Ni͑pao͒ 2 ͑L͒ 2 ͔͑A͒ 2 ͑L: intrachain attaching ligand of Ni II ion; A −1 : interchain counteranion͒ is a ferromagnetic one-dimensional network system with repeating units of the Mn III-Ni II-Mn III trimer which itself behaves as a single-molecule magnet with an S = 3 spin ground state and negative uniaxial single-ion anisotropy ͑D͒ parallel to the bridging direction. The slow relaxation of the magnetic moment in this SCM system originates in an energy barrier for spin reversal ͑⌬E͒, which is closely related to the ferromagnetic interaction between the trimers ͑J trimer ͒ as well as to the D of the trimer. We have investigated the effects of pressure on three compounds representative of the above SCM family through ac susceptibility measurements under hydrostatic pressures up to P = 13.5 kbar and crystal structural analysis experiments up to P = 20.0 kbar, and have observed a pronounced enlargement of ⌬E when J was artificially increased. The application of hydrostatic pressure brought about the systematic enhancement of ⌬E ͑a maximum increase of 10% within the pressure region of the experiments͒. The pressure dependence of ⌬E varied according to the kind of attaching ligand L involved and the intrachain structure, and we have experimentally found that isotropic lattice shrinkage is desirable if a continuous increase of ⌬E in this system is aimed at.
We synthesized NiO nanoparticles
in the pores of mesoporous silica,
with particle sizes ranging from 2.6 to 22 nm, and investigated their
crystal structure and magnetic properties. The size dependence of
the crystal structure exhibited a change in behavior across the critical
size of 3 nm. The lattice constants attained maximal values at approximately
3 nm and asymptotically decreased with increasing particle size, reaching
the values for the bulk crystal. The rhombohedral distortion of crystallographic
structure increased with decreasing particle size for particle sizes
below ≈10 nm and was maximum at ≈3 nm. The size dependence
of lattice strain also exhibited a maximum at 3 nm. The magnetic properties
such as the coercive field, anisotropy energy, blocking temperature,
and shell moment exhibited maxima for particle sizes between 3 and
10 nm. These results suggest that the magnetic behavior is generated
by the change in the magnetic anisotropy constant originating from
the changes in the crystal structure.
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