Diamond-like carbon (DLC)-coated cotton textiles showing both superhydrophobic and superoleophilic properties exhibit highly controllable, energy-efficient oil–water separation.

A self-consistent theory of the current-induced switching of magnetization using nonequilibrium Keldysh formalism is developed for a junction of two ferromagnets separated by a nonmagnetic spacer in the ballistic limit. It is shown that the spin-transfer torques responsible for current-induced switching of magnetization can be calculated from first principles in a steady state when the magnetization of the switching magnet is stationary. A steady state is achieved when the spin-transfer torque, proportional to bias voltage in the linear response regime, is balanced by the torque due to anisotropy fields. The spin-transfer torque is expressed in terms of one-electron surface Green functions for the junction cut into two independent parts by a cleavage plane immediately to the left and right of the switching magnet. The surface Green functions are calculated using a tight-binding Hamiltonian with parameters determined from a fit to an ab initio band structure. This treatment yields the spin transfer torques taking into account rigorously contributions from all the parts of the junction. The spin-transfer torque has two components, one with the torque vector T ʈ in the plane containing the magnetizations of the two magnetic layers and another with the torque vector T Ќ perpendicular to this plane. It is shown that, in general, T ʈ and T Ќ may be comparable in magnitude and they both tend to finite values independent of the spacer thickness in the limit of a thick spacer. T Ќ is shown to be small when the exchange splitting of the majority-and minority-spin bands in both ferromagnets tends to infinity or in the case when the junction has a plane of reflection symmetry at the center of the spacer. The torques T Ќ and T ʈ are comparable for a Co/ Cu/ Co͑111͒ junction when the switching Co layer is one or two atomic planes thick. T Ќ is Ϸ27% of T ʈ even for a switching Co magnet of ten atomic planes. Depending on material parameters of the junction, the relative sign of T Ќ and T ʈ can be negative as well as positive. In particular, T Ќ / T ʈ Ͻ 0 for Co/ Cu/ Co͑111͒ with switching Co magnet of one atomic plane and T Ќ / T ʈ Ͼ 0 for two atomic planes of Co. A negative sign of the ratio T Ќ / T ʈ has a profound effect on the nature of switching, particularly in the realistic case of easy-plane ͑shape͒ anisotropy much larger than in-plane uniaxial anisotropy. To calculate the hysteresis loops of resistance versus current, and hence to determine the critical current for switching, the microscopically calculated spintransfer torques are used as an input into the phenomenological Landau-Lifshitz equation with Gilbert damping. In the absence of an applied magnetic field, an ordinary hysteresis loop is the only possible switching scenario when T Ќ / T ʈ Ͼ 0. However, for T Ќ / T ʈ Ͻ 0, a normal hysteretic switching occurs only at relatively low current densities. When the current exceeds a critical value, there are no stable steady states and the system thus remains permanently in a time dependent state. This is analogous to th...

The crystal and molecular structure of the layered weak-ferromagnet Fe[CH(3)PO(3)] x H(2)O has been solved by X-ray single-crystal diffraction techniques. Crystal data for Fe[CH(3)PO(3)] x H(2)O are the following: orthorhombic space group Pna2(1); a =17.538(2), b = 4.814(1), c = 5.719(1) A. The structure is lamellar, and it consists of alternating organic and inorganic layers along the a direction of the unit cell. The inorganic layers are made of Fe(II) ions octahedrally coordinated by five phosphonate oxygen atoms and one from oxygen of the water molecule. Each phosphonate group coordinates four metal ions, through chelation and bridging, making in this way a cross-linked Fe-O network. The resultant layers are then separated by bilayers of the methyl groups, with van der Waals contacts between them. The compound is air stable, and it dehydrates under inert atmosphere at temperatures above 120 degrees C. The oxidation state of the metal ion is +2, and the electronic configuration is d(6)( )()high spin (S = 2), as determined from dc magnetic susceptibility measurements from 150 K to ambient temperature. Below 100 K, the magnetic moment of Fe[CH(3)PO(3)] x H(2)O rises rapidly to a maximum at T(max) approximately equal to 24 K, and then it decreases again. The onset of peak at T = 25 K is associated with the 3D antiferromagnetic long-range ordering, T(N). The observed critical temperature, T(N), is like all the other previously reported Fe(II) phosphonates, and it appears to be nearly independent of the interlayer spacing in this family of hybrid organic-inorganic layered compounds. Below T(N), the compound behaves as a "weak ferromagnet", and represents the third kind of magnetic materials with a spontaneous magnetization below a finite critical temperature, ferromagnets and ferrimagnets being the other two types.

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A new series of chromium(II)-alkylphosphonates, Cr[RPO 3 ]‚H 2 O (R ) CH 3 , C 2 H 5 ), and chromium(II) ethylenebis(phosphonate), Cr 2 [O 3 P-(CH 2 ) 2 -PO 3 ]‚3H 2 O, have been synthesized by reaction of CrCl 2 and the corresponding phosphonic acid in water in the presence of urea. The (2-aminoethyl)phosphonic acid reacts with CrCl 2 to give an unexpected compound of formula Cr[H 3 N-(CH 2 ) 2 -PO 3 (Cl)]. All the compounds are sensitive to the air, except for the latter one. They were characterized by X-ray powder diffraction, thermogravimetry, and UV-visible and infrared spectroscopy, and their magnetic properties were studied by a SQUID magnetometer. The metal ion is in the high-spin d 4 configuration, and it appears to have an octahedral coordination. Cr[CH 3 PO 3 ]‚H 2 O behaves as a "weak" ferromagnet, with a Ne `el temperature of T N ) 35 K, and it represents an example of an unusual kind of molecular-based magnetic material, having a finite zero-field magnetization. The thermal variation of the magnetic susceptibility of Cr 2 [O 3 P-(CH 2 ) 2 -PO 3 ]‚3H 2 O follows the Curie-Weiss law, with a large negative Weiss constant of θ ) -73 K. Below 100 K, the susceptibility increases until a peak at T N ) 15 K is observed, and this is associated to the threedimensional antiferromagnetic order. Cr[H 3 N-(CH 2 ) 2 PO 3 (Cl)] is paramagnetic down to 5 K.

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