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First-principles calculations of the magnetic anisotropic constants of Co–Pd multilayers: Effect of stacking faults¹
by G. Wu, K. H. Khoo, M. H. Jhon, H. Meng, S. Y. H. Lua, R. Sbiaa & C. K. Gan

“Using first-principles density functional theory calculations with spin-orbit coupling, we systematically investigate the magnetic anisotropic energy (MAE) of Co_nPd_m (n+m=5) magnetic multilayers. We consider the influences of the relative atomic weight of Co, w_Co, stacking fault, and external stress on the MAE. We find that out-of-plane lattice constant, saturation magnetization, and magnetic moments are almost linearly correlated with w_Co. The magnetic anisotropic constant (MAC) curve of Co_nPd_m without stacking fault shows a near-linear dependence on w_Co that agrees with our derived effective MAC K_u^eff which includes shape, magneto-crystalline, and magneto-elastic contributions. We also show that the contributions from Pd layers to both the total magnetic moments and magnetic anisotropy are significant. The stress anisotropy due to the substrate has a weak effect on the MAC. However the stacking fault has a strong effect on the MAC. When the Co layer is thin, a Co–Pd interface without stacking fault is necessary for higher K_u^eff. However, when the Co layer is thick, creating stacking faults inside the Co region may produce a larger K_u^eff. Our study suggests the ways to increase the perpendicular magnetic anisotropy in Co–Pd multilayer systems and subsequently leads to the development of novel magnetic recording devices….”

Mn local moments prevent superconductivity in iron pnictides Ba(Fe_1−xMn_x)₂As₂²
by Y. Texier, Y. Laplace, P. Mendels, J. T. Park, G. Friemel, D. L. Sun, D. S. Inosov, C. T. Lin & J. Bobroff

“⁷⁵As nuclear magnetic resonance (NMR) experiments were performed on Ba(Fe_1−xMn_x)₂As₂ (x_Mn = 2.5%, 5% and 12%) single crystals. The Fe layer magnetic susceptibility far from Mn atoms is probed by the ⁷⁵As NMR line shift and is found similar to that of BaFe₂As₂, implying that Mn does not induce charge doping. A satellite line associated with the Mn nearest neighbours (n.n.) of ⁷⁵As displays a Curie-Weiss shift which demonstrates that Mn carries a local magnetic moment. This is confirmed by the main line broadening typical of a RKKY-like Mn-induced staggered spin polarization. The Mn moment is due to the localization of the additional Mn hole. These findings explain why Mn does not induce superconductivity in the pnictides contrary to other dopants such as Co, Ni, Ru or K…”

Radiation-dominated era and the power of general relativity³
by C. Corda

“An analysis in the framework of the radiation-dominated era permits to put bounds on the weak modification of general relativity which arises from the Lagrangian R^1+ε. Such a theory has been recently discussed in various papers in the literature. The new bounds together with previous ones in the literature rule out this theory in an ultimate way…”

1. Wu, G. (2012-06-28) First-principles calculations of the magnetic anisotropic constants of Co. EPL (Europhysics Letters), 10(1), 3769. DOI: 10.1209/0295-5075/99/17001 [↩]
2. Y. Texier, Y. Laplace, P. Mendels, J. T. Park, G. Friemel, D. L. Sun, D. S. Inosov, C. T. Lin, & J. Bobroff. (2012) Mn local moments prevent superconductivity in iron-pnictides Ba(Fe_1-xMn_x)₂As₂. Europhys. Lett. 99 17002 (2012). DOI: 10.1209/0295-5075/99/17002 [↩]
3. Corda, Christian. (2012-07-09) Radiation-dominated era and the power of general relativity. EPL (Europhysics Letters), 148(1), 1. DOI: 10.1209/0295-5075/99/10001 [↩]

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