Magneto-electro-elastic effects in some rare earth molybdates and related properties

Abstract

A giant magneto-electric effect was observed in single-crystal samples of metastable orthorhombic ferro-electric ferro-elastic paramagnetic beta ' phases of rare earth molybdates Tb2(MoO4)3 and TbGd(MoO4)3. The electric polarization in these compounds showed large and sharp changes in pulsed magnetic fields of 100 kOe at 78 K. Magnetic fields applied in a certain direction produced irreversible alterations in ferro-electric domain structure of these compounds that were observed visually. This effect was explained qualitatively in terms of large spin-orbit coupling in rare earth triply positive-charged ions and of interaction between the crystal field and the anisotropic charge density cloud of 4f electrons of rare earth triply charged ions of non-zero angular momentum. Related anomalies in the magnetostriction and in magnetization were also observed. The photoluminescence related to Tb3+ ions was observed at temperatures in the range 4.2-300 K. The most intense photoluminescence takes place in the green part of the spectrum. Here two groups of narrow sharp lines were observed, each group consisting of three lines. The photoluminescence exhibited a strong dependence of the polarization upon the ferro-electric domain orientation. Some applications of the effect are proposed.

Magnetic switching of ferroelectric domains at room temperature in multiferroic PZTFT

“…Nevertheless, the possibility of ferroelectric switching using a magnetic field at room temperature has been successfully demonstrated. Not all of the domains had changed after the magnetic field had been applied, but this is in keeping with work by Ponomarev et al 33. on Tb 2 (MnO 4 ) 3 .…”

Magnetoelectric and Magnetostrictive Effects in Scheelite-Type HoCrO4

“…As shown in the inset of Figure b, the directions of field-induced Δ L and Δ P are, respectively, parallel and perpendicular to the external magnetic field. One can infer that the field-induced mechanical strain by the spin–lattice coupling may affect the polarization by rotating the polarized domains, as demonstrated by the Yb 3+ complex and Tb 2 (MoO 4 ) 3 compounds. , For scheelite-type HoCrO 4 , the domain switching coupling is nearly absent below μ 0 H C . However, the induced P emerges even though the deformation is negligible.…”

“…In addition to the specific magnetic and electric properties, the ME coupling may also be related to strain or magnetostriction. , In the well-studied ME multiferroic TbMn 2 O 5 , the magnetostrictive (MS) effect due to the Tb 3+ spin alignment plays an important role in the low field ME coupling . It is worth noting that even without long-range magnetic order, the ME effect can be achieved by magnetostriction of rare-earth ions. , In Tb 2 (MnO 4 ) 3 , P can be actuated largely by a pulse magnetic field through the MS effect, where the anisotropic 4f-electron cloud of terbium ions, tied to the magnetic moment via the strong spin–orbital coupling, perturbs the crystal lattice and thus changes the spontaneous P . The single-crystal holmium shows a gigantic MS effect with the coefficient, defined as the fractional change in length under an applied magnetic field, up to 3500 ppm at 45 K as a result of the strong spin–orbital and spin–lattice coupling .…”

Structural Domain Switching by Magnetic Fields in RAl3C3 (R = Rare Earth)

“…One is Tb 2 (MoO 4 ) 3 , where the crystal axes are interchanged by the field. 12 This phenomenon can be understood as being caused by a strong magnetoelastic coupling through the quadrupole moment. When a magnetic field is applied, the quadrupole moment is induced in the 4f orbital.…”