Interplay of 4f-3d Magnetism and Ferroelectricity in DyFeO3

DyFeO3 exhibits a weak ferromagnetism (TNFe ~ 645 K) that disappears below a spin-reorientation (Morin) transition at TSRFe ~ 50 K. It is also known that applied magnetic field induces ferroelectricity at the magnetic ordering temperature of Dy-ions (TNDy ~ 4.5 K). Here, we show that the ferroelectricity exists in the weak ferromagnetic state (TSRFe < T < TN,C) without applying magnetic field, indicating the crucial role of weak ferromagnetism in inducing ferroelectricity. 57Fe M\"ossbauer studies show that hyperfine field (Bhf) deviates from mean field-like behaviour that is observed in the weak ferromagnetic state and decreases below the onset of spin-reorientation transition (80 K), implying that the Bhf above TSR had additional contribution from Dy-ions due to induced magnetization by the weak ferromagnetic moment of Fe-sublattice and below TSR, this contribution decreases due to collinear ordering of Fe-sublattice. These results clearly demonstrate the presence of magnetic interactions between Dy(4f) and Fe(3d) and their correlation with ferroelectricity in the weak ferromagnetic state of DyFeO3.Comment: 5 pages, 6 figures, published in EP

Decompositions of a C

We prove that if A is a C-algebra, then for each a∈A, Aa={x∈A/x≤a} is itself a C-algebra and is isomorphic to the quotient algebra A/θa of A where θa={(x,y)∈A×A/a∧x=a∧y}. If A is C-algebra with T, we prove that for every a∈B(A), the centre of A, A is isomorphic to Aa×Aa′ and that if A is isomorphic A1×A2, then there exists a∈B(A) such that A1 is isomorphic Aa and A2 is isomorphic to Aa′. Using this decomposition theorem, we prove that if a,b∈B(A) with a∧b=F, then Aa is isomorphic to Ab if and only if there exists an isomorphism φ on A such that φ(a)=b

Experimental observation of quantum corrections to electrical resistivity in nanocrystalline soft magnetic alloys

X-ray diffraction patterns of nanocrystalline Fe-Cu-Nb-Si-B (FINEMET) alloys reveal that bcc &#945;-Fe/&#945; -FeSi crystallites with the average grain size of 20(5) nm are dispersed in amorphous matrix. Enhanced electron-electron interaction (EEI) and quantum interference (QI) effects as well as electron-magnon (and/or electron-spin fluctuation) scattering turn out to be the main mechanisms that govern the temperature dependence of resistivity. Of all the inelastic scattering processes, inelastic electron-phonon scattering is the most effective mechanism to destroy phase coherence of electron wave functions. The diffusion constant, density of states at the Fermi level and the inelastic scattering time have been estimated, for the first time, for the alloys in question