Magnetic ferroelectrics or multiferroics, which are currently extensively explored, may provide a good arena to realize a novel magnetoelectric function. Here we demonstrate the genuine electric control of the spiral magnetic structure in one of such magnetic ferroelectrics, TbMnO3. A spinpolarized neutron scattering experiment clearly shows that the spin helicity, clockwise or counterclockwise, is controlled by the direction of spontaneous polarization and hence by the polarity of the small cooling electric field.Electric control of magnetic spins or their ordering structure has long been a big challenge in condensed matter physics. Furthermore, manipulating the magnetization by electric field may provide a low energy-consuming way in spin-electronics and a higher data density in information storages [1,2]. There are a number of magnetoelectric materials whose magnetization can be changed, though minutely, with an external electric field, yet only a very few are known whose magnetic structure itself can be controlled by an electric field [1,3,4,5]. The use of ferroelectricity is perhaps indispensable to enhance the electric field action on the magnetic spins. [2] One of the robust mechanisms to produce the ferroelectricicty of magnetic origin has been recently proposed by Katsura, Nagaosa, and Balatsky (KNB) [6]. The overlap of the electronic wave function between the two atomic sites (i and i + 1) with mutually canted spins (S i and S i+1 ) can generate electric polarization,, where e i,i+1 denotes the unit vector connecting the two sites and A is a constant determined by the spin exchange interaction and the spin-orbit interaction. (Note that the similar theoretical results have been obtained independently also in refs. [7,8]). In case the transverse-spiral (cycloidal) spin order is realized ( Fig. 1(b)), the uniform spontaneous polarization is expected to emerge as the sum of the local polarization p i in the direction perpendicular to the spiral propagation vector and the vector chirality,). This spin-driven ferroelectricity has recently been found in several transversespiral magnets such as TbMnO 3 (ref.[9]), Ni 3 V 2 O 8 (ref.[10]), MnWO 4 (ref.[11]), and also in a transverse conespiral magnet CoCr 2 O 4 (ref.[12]). We report here the quantitative elucidation of such magnetically induced ferroelectricity in terms of the spin ellipticity as the order parameter and show the successful electric control between the clockwise (CW) and counter-clockwise (CCW) spin helixes.A family of perovskite manganites, RMnO 3 with R being Tb, Dy, and their solid solution, have recently been demonstrated to undergo a ferroelectric transition at the Curie temperature T C of 20 − 30 K (see the example shown in Fig. 1(c)) [13,14]. Below T N ∼ 40 K, the compounds undergo a long-range spin ordering with the modulation vector Q s = (0, ±q, 1) with q = 1/2 − 1/4 (in P bnm orthorhombic setting) [9,15]. This has been ascribed to the spin frustration effect caused by the combination of GdFeO 3 -type distortion and staggered orbital or...

The site-specific incorporation of cross-linkable designer amino acids into proteins is useful for covalently bonding protein complexes upon exposure to light. This technology can be used to study networks of protein-protein interactions in living cells; however, to date it has only been applicable for use with a narrow range of cell types, due to the limited availability of plasmid-based transfection protocols. In the present study, we achieved adenovirus-based expression of a variant of an archaeal pyrrolysyl-tRNA synthetase and UAG-recognising tRNA pair, which was used to incorporate unnatural amino acids into proteins at sites defined by in-frame UAG codons within genes. As such, the site-specific photo-cross-linking method is now applicable to a wide variety of mammalian cells. In addition, we repositioned the reactive substituent of a useful photo-cross-linker, Nε-(para-trifluoromethyl-diazirinyl-benzyloxycarbonyl)-l-lysine (pTmdZLys), to the meta position, which improved its availability at low concentration. Finally, we successfully applied this system to analyse the formation of a protein complex in response to a growth signal in human cancerous cells and human umbilical vein endothelial cells. This adenovirus-based system, together with the newly designed cross-linkable amino acid, will facilitate studies on molecular interactions in various cell lines of medical interest.

In this paper, we irradiated the millijoule−level THz−FEL pulses on ferromagnetic domains of ErFeO 3 single crystal. We found that magnetic domain shapes can be permanently reconfigured upon irradiation by THz-FEL, without causing permanent damage in the sample. The process could be explained by the combination of ultrafast heating−induced depinning effect and entropic force due to local thermal gradient. Our result demonstrates the potential of THz−FEL as a novel light source for the investigation of thermally induced spin dynamics in the THz region, and paves way for the THz spintronic devices in future.

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