Rare-earth impurities in Co2_2MnSi: an opportunity to improve Half-Metallicity at finite temperatures

We analyse the effects of doping Holmium impurities into the full-Heusler ferromagnetic alloy Co$_2$MnSi. Experimental results, as well as theoretical calculations within Density Functional Theory in the "Local Density Approximation plus Hubbard U" framework show that the holmium moment is aligned antiparallely to that of the transition metal atoms. According to the electronic structure calculations, substituting Ho on Co sites introduces a finite density of states in the minority spin gap, while substitution on the Mn sites preserves the half-metallic character.Comment: 22 pages, 8 figures. published in PR

The Religious Value of Language between the Sacred and the Holy

Throughout the 19th and 20th centuries, language undoubtedly constituted a strong topic of philosophical interest both in Eastern Europe and in the West. Following in particular Florensky’s conception of speech and language as living organisms structured in an antinomic way, we come to grasp their fundamental symbolic meaning. According to a gradual development of increasing semantic depth, the symbolism rises from a common word to a poetic-religious word, which sings of the splendour of the Saint. Likewise, language and poetry are for Heidegger fundamental forms of the event of being and of his truth, which manifests itself as sacred. Here then is the need for a basic decision to emerge, between the inevitable uncertainty due to the concealment of the sacred, and a possible apophaticism which, without exhausting its Essence, knows it can name the Saint.Throughout the 19th and 20th centuries, language undoubtedly constituted a strong topic of philosophical interest both in Eastern Europe and in the West. Following in particular Florensky’s conception of speech and language as living organisms structured in an antinomic way, we come to grasp their fundamental symbolic meaning. According to a gradual development of increasing semantic depth, the symbolism rises from a common word to a poetic-religious word, which sings of the splendour of the Saint. Likewise, language and poetry are for Heidegger fundamental forms of the event of being and of his truth, which manifests itself as sacred. Here then is the need for a basic decision to emerge, between the inevitable uncertainty due to the concealment of the sacred, and a possible apophaticism which, without exhausting its Essence, knows it can name the Saint

Al-Substitution Effects on Physical Properties of the Colossal Magnetoresistance Compouns La0.67ca0.33mno3

We present a detailed study of the polycrystalline perovskite manganites La0.67Ca0.33AlxMn1-xO3 (x = 0, 0.1, 0.15, 0.5) at low temperatures and high magnetic fields, including electrical resistance, magnetization, ac susceptibility. The static magnetic susceptibility was also measured up to 1000 K. All the samples show colossal magnetoresistance behavior and the Curie temperatures decrease with Al doping. The data suggest the presence of correlated magnetic clusters near by the ferromagnetic transition. This appears to be a consequence of the structural and magnetic disorder created by the random distribution of Al atoms.Comment: 13 pages including 5 figure

Observation of a Griffiths-like phase in the paramagnetic regime of ErCo_2

A systematic x-ray magnetic circular dichroism study of the paramagnetic phase of ErCo2 has recently allowed to identify the inversion of the net magnetization of the Co net moment with respect to the applied field well above the ferrimagnetic ordering temperature, Tc. The study of small angle neutron scattering measurements has also shown the presence of short range order correlations in the same temperature region. This phenomenon, which we have denoted parimagnetism, may be related with the onset of a Griffiths-like phase in paramagnetic ErCo2. We have measured ac susceptibility on ErCo2 as a function of temperature, applied field, and excitation frequency. Several characteristics shared by systems showing a Griffiths phase are present in ErCo2, namely the formation of ferromagnetic clusters in the disordered phase, the loss of analyticity of the magnetic susceptibility and its extreme sensitivity to an applied magnetic field. The paramagnetic susceptibility allows to establish that the magnetic clusters are only formed by Co moments as well as the intrinsic nature of those Co moments

Non-quasiparticle states in Co2_2MnSi evidenced through magnetic tunnel junction spectroscopy measurements

We investigate the effects of electronic correlations in the full-Heusler Co$_2$MnSi, by combining a theoretical analysis of the spin-resolved density of states with tunneling-conductance spectroscopy measurements using Co$_2$MnSi as electrode. Both experimental and theoretical results confirm the existence of so-called non-quasiparticle states and their crucial contribution to the finite-temperature spin polarisation in this material.Comment: Repalced Fig. 1. of PRL, 100, 086402 (2008), better k-space resolution for DOS around Fermi energ