Magnetic Origin of Giant Magnetoelectricity in Doped Y-type HexaferriteBa0.5Sr1.5Zn2(

Abstract

We investigated site-specific magnetic behaviors of multiferroic Ba 0.5 Sr 1.5 Zn 2 ðFe 1−x Al x Þ 12 O 22 using Fe L 2;3 -edge x-ray magnetic circular dichroism. The Al dopants mostly replace the Fe 3þ ions at octahedral (O h ) sites, which contribute unquenched angular momenta through off-centering displacements. This replacement greatly reduces the magnetic anisotropy energy to change the magnetic order from a helical to a heliconical type with enhanced magnetoelectric susceptibility (α ME ). The tetrahedral (T d ) Fe sites exhibit magnetic hysteresis distinguishable from that of the O h sites, especially at low magnetic fields. These results provide essential clues for the heliconical order with a giant α ME and multibit memory effects in the Al-doped Y-type hexaferrite. Multiferroic materials, in which magnetism and ferroelectricity coexist with a cross coupling, the so-called magnetoelectric (ME) effect, have been intensively studied experimentally and theoretically over the past decade due to their potential technological applications as nextgeneration multibit memory devices [1][2][3]. The ME effect was demonstrated in various multiferroic materials such as chromates, manganites, ferrites, etc. [1-6], and spiral, cycloidal, or noncollinear helical magnetic orders were known to be essential for a large ME effect [7][8][9][10][11]. Multiferroicity is well explained by an inverse Dzyaloshinskii-Moriya interaction [12,13] or a spin-current model [14]. However, most of the materials were recognized to face the difficulty of application barriers due to the low ME response, low ME temperature, and/or the requirement of a high magnetic field. Recently, hexaferrites with several different types have attracted much attention as candidates for possible multiferroic application materials with a giant ME susceptibility (α ME ) at a relatively high temperature [4,[15][16][17], and even nonvolatile multistate behaviors were demonstrated at room temperature [18]. Particularly in Y-type hexaferrites ðBa; SrÞ 2 Zn 2 Fe 12 O 22

Magnetoelectricity in multiferroic hexaferrites as understood by crystal symmetry analyses

“…However, due to the quenched orbital moments in the tetrahedral and centered octahedral 31 , the p-d hybridization in Me5-8 and Me10 would be very weak, leading to the negligible polarization by this mechanism. But, the off-center Fe/Co in octahedral can induce large orbital moments 31 which may enhance the extent of p-d hybridization. Therefore, Me3, Me4, and Me9 sites may provide larger a0 and subsequently larger P via the p-d hybridization mechanism.…”

“…31 , the p-d hybridization in Me5-8 and Me10 would be very weak, leading to the negligible polarization by this mechanism. But, the off-center Fe/Co in octahedral can induce large orbital moments31 which may enhance the extent of p-d…”

4D visualization of the light-induced coherent magnon by an X-ray free electron laser

“…It is well known that these calculations are accurate for X-ray energies away from the absorption edge. To estimate the penetration depth at the edge at 711 eV more precisely, we take into account the intensity ratio ~9.26 of the XAS spectrum 54 at the pre-edge and the absorption edge. The penetration depth is deduced to be 39 nm from dividing the depth at Ei = 702 eV by the XAS intensity ratio.…”

Multiferroic materials and magnetoelectric physics: symmetry, entanglement, excitation, and topology

“…Furthermore, Chun et al found that the critical magnetic field for switching a polarization can be significantly reduced from 1.0 T down to 1.0 mT in a properly Al-substituted system, as shown in Ba 0.5 Sr 1.5 Zn 2 (Fe 1−x Al x ) 12 O 22 [210,211]. A giant magnetoelectric susceptibility was observed in the sample with x = 0.08.…”