Magnetism and effect of anisotropy with one dimensional monatomic chain of cobalt by a Monte Carlo simulation

The magnetic properties of the one dimensional (1D) monatomic chain of Co reported in a previous experimental work are investigated by a classical Monte Carlo simulation based on the anisotropic Heisenberg model. In our simulation, the effect of the on-site uniaxial anisotropy, Ku, on each individual Co atom and the nearest neighbour exchange interaction, J, are accounted for. The normalized coercivity HC(T)/HC(TCL) is found to show a universal behaviour, HC(T)/HC(TCL) = h0(e^{TB/T}-e) in the temperature interval, TCL < T < TBCal, arising from the thermal activation effect. In the above expression, h0 is a constant, TBCal is the blocking temperature determined by the calculation, and TCL is the temperature above which the classical Monte Carlo simulation gives a good description on the investigated system. The present simulation has reproduced the experimental features, including the temperature dependent coercivity, HC(T), and the angular dependence of the remanent magnetization, MR(phi,theta), upon the relative orientation (phi,theta) of the applied field H. In addition, the calculation reveals that the ferromagnetic-like open hysteresis loop is a result of a slow dynamical process at T < TBCal. The dependence of the dynamical TBCal on the field sweeping rate R, the on-site anisotropy constant Ku, and the number of atoms in the atomic chain, N, has been investigated in detail.Comment: 20 pages, 7 figures included, J Phys Condens Matter, In Pres

90 degree polarization rotator using a bilayered chiral metamaterial with giant optical activity

A bilayered chiral metamaterial (CMM) is proposed to realize a 90 degree polarization rotator, whose giant optical activity is due to the transverse magnetic dipole coupling among the metallic wire pairs of enantiomeric patterns. By transmission through this thin bilayered structure of less than \lambda/30 thick, a linearly polarized wave is converted to its cross polarization with a resonant polarization conversion efficiency (PCE) of over 90%. Meanwhile, the axial ratio of the transmitted wave is better than 40 dB. It is demonstrated that the chirality in the propagation direction makes this efficient cross-polarization conversion possible. The transversely isotropic property of this polarization rotator is also experimentally verified. The optical activity of the present structure is about 2700 degree/\lambda, which is the largest optical activity that can be found in literature.Comment: 16 pages, 4 figure