Spin Parity Effect on Magnetic Relaxation by Quantum Tunneling in Nanomagnets

Spin parity effect on magnetic relaxation by quantum tunneling in the biaxial spin model is studied by taking into account the transverse local stray field. It is shown that the square root time dependence in the even resonance occurs in the presence of a distribution of transverse anisotropic parameters, while the odd resonance always shows exponential relaxation. Magnetic relaxation under a sweeping field is also studied. The variation of the relaxation curve with the increasing distribution width of the local stray field for even resonance is qualitatively different from that of the odd resonance. The theoretical result on even resonance is in agreement with experimental results on Fe8 system, while the prediction for odd resonance awaits the experimental verification.

Enhancing single-molecule magnet behavior of linear Co~Ⅱ-Dy~Ⅲ-Co~Ⅱ complex by introducing bulky diamagnetic moiety

Single-molecule magnets （SMMs） are regarded as promising candidates for ultrahigh-density storage, quantum information processing and molecular spintronics. It is a crucial challenge for chemists to modulate magnetic dynamics of SMMs. Here, we successfully synthesized two 3d-4f polynuclear compounds [Co2Dy（TTTTCl）2（MeOH）]NO3.3MeOH （1） and [Co2Dy（TTTTCl）2 （MeOH）][Co（HTTTTCl）]（NO3）z-2.5MeOH＇2H20 （2）, where H3TTTTCl=2,2＇,2＂-（（（nitrilotris（ethane-2,1-diyl）） tris（azanediyl）） tris（methylene））tris-（4-chlorophenol）. On applying the approach by co-crystallization of bulky diamagnetic moiety, the effective energy barrier enhances from 401 K （1） to 536 K （2）, which are both among the highest d-f heterometallic SMMs.

Effective Approach for the Synthesis of Monodisperse Magnetic Nanocrystals and M-Fe3O4 （M = Ag, Au, Pt, Pd） Heterostructures

Monodisperse and size-tunable magnetic iron oxide nanoparticles （NPs） have been synthesized by thermal decomposition of an iron oleate complex at 310 ℃ in the presence of oleylamine and oleic acid. The diameters of the as-synthesized iron oxide NPs decrease with increasing concentrations of iron oleate complex and oleic acid/oleylamine. In addition, the size-dependent crystallinity and magnetic properties of iron oxide NPs are presented. It is found that larger iron oxide NPs have a higher degree of crystallinity and saturation magnetization. More importantly, various M-iron oxide heterostructures （M = Au, Ag, Pt, Pd） have been successfully fabricated by using the same synthesis procedure. The iron oxide NPs are grown over the pre-made metal seeds through a seed-mediated growth process. The physicochemical properties of Au-Fe3O4 heterostructures have been characterized by X-ray diffraction （XRD）, superconducting quantum interference device （SQUID） magnetometry and UV-vis spectroscopy. The as-synthesized Au-Fe3O4 heterostructures show a red-shift in surface plasmon resonance peak compared with Au NPs and similar magnetic properties to Fe3O4 NPs. The heterojunction effects present in such nanostructures offer the opportunity to tune the irphysicochemical properties. Therefore, this synthesis process can be regarded as an efficient way to fabricate a series of heterostructures for a variety of applications.

Low-temperature antiferromagnetic order of Ni_4 single-molecule magnets

The low-temperature specific heat of Ni4 single-molecule magnets (SMMs) is measured in a PPMS He-3 system. The tem- perature-dependent specific heat of Ni4 SMMs shows an antiferromagnetic phase transition at 0.91 K. The experimental results are in good consistency with Monte Carlo simulation of 3D-Ising model, indicating two independent diamond-like antiferro-magnetic structures with an exchange energy J = 0.020 K in Ni4 system.

Pressure-induced changes in the magnetic properties of the single crystal of Mn_3 single-molecule magnet

The magnetic measurements of the single crystal of Mn3 single-molecule magnet under high pressure at T=2 K have been performed.We find both the antiferromagnetic intermolecular coupling parameter J and the effective energy barrier to vary compared with the measurements at low pressure.The increase of|J|is estimated to be 12%at 0.7 GPa when compared with that of0 GPa,whereas the effective energy barrier becomes smaller with increasing pressure.Our results demonstrate that the intermolecular interaction of single-molecule magnet can be changed by pressure.Compared with the normal magnetic alloy,the effect of pressure on the magnetic properties of Mn3 is much more prominent,which implies that Mn3 may have great potential in magnetic multifunctional material.