Magnetoelectric effect inGd2CuO4

Abstract

The magnetoelectric (ME) efFect is observed in the tetragonal antiferromagnet GdqCu04 in magnetic fields up to 7 T. This is an observation of the ME effect in the class of tetragonal crystals with the general formula RqCu04 (R =rare earth), which are parent compounds for high-T, superconductivity. The ME effect is shown to exist only below the ordering temperature of the rare-earth magnetic subsystem at T~(Gd)= 6.5 K ln accordance with results based on a symmetry analysis.The field and temperature dependence of the effect confirm the magnetic structure revealed recently in this compound.The magnetic properties of the R~Ce Cu04 (R=rare-earth ion) compounds, which belong to the family of recently discovered high -T, superconductors with electron -type conductivity, have been intensively investigated during the last few years, following the suggestion that the antiferromagnetism of the Cu02 planes plays an important role in the superconductivity of these compounds. In fact, the rare-earth subsystem is also of importance in the magnetism of these materials. Unlike in R-Ba-Cu-0 compounds where the substitution of trivalent rare earths had little effect on their superconductivity, in electron-doped R2 Ce Cu04 compounds the rare-earth subsystem affects strongly both magnetic and superconducting properties. According to Refs. 3 -6, the superconductivity of R2 Ce Cu04 is observed only for compounds containing light rare-earth ions (R =Nd, Sm, Eu, and Pr), and no superconductivity is observed in compounds with heavier rare-earth ions, starting &om Gd. Also investigations of the upper critical Geld H, 2 of Smq 85Ceo i5Cu04 give indications for an infiuence of the magnetic ordering of the rare-earth ions on the superconducting state. ' It is therefore of main concern to elucidate the role of the rare-earth ions in forming the electronic properties of R2 Ce Cu04 and of the parent compound R2Cu04.Gd2Cu04 occupies a unique place in the family of electron doped high -T superconducting materials due to a number of unusual magnetic properties.In addition, a ferromagnetic ordering of the rare-earth spins within the (a, b) layers, which are parallel to the Cu02 layers, has been detected in Gd~Cu04 by means of neutron scattering. Considering the possible correlation between nonsuperconducting and magnetic properties of Gd2Cu04 we looked for an independent method of studying the magnetic properties of the Gd spin system in Gd2Cu04. Therefore, we have undertaken a systematic search for the magnetoelectric effect in this material, the existence of which is directly related to the symmetry properties of the magnetic structure in Gd2Cu04. In this paper we present experimental results of the magnetic 6eld induced electric polarization in Gd2Cu04, which, to our knowledge, magnetoelectric effect has not been observed before in any compound with the general formula R2Cu04.The magnetic structure of Gd2Cu04 includes two magnetic subsystems (copper and rare earth) with essentially different magnetic properties. The Cu spins become antiferromagne...

Magnetoelectric studies of antiferromagnetic crystals in strong magnetic fields

“…It is the possible correlation between "nonsuperconducting" and magnetic properties that attracted attention to the magnetic subsystem of this compound. Gd2CuO4 was the first member of the family to exhibit a ME effect and the experimental results helped to clarify the magnetic ground state in this compound [15].…”

Magnetoelectric effect and magnetic dynamics in the Gd2CuO4 antiferromagnet

“…The authors of [8] conclude that the gadolinium and copper sublattices are ordered with the same wave vector. However, this conclusion does not agree with an analysis of the magnetic order ing in Gd 2 CuO 4 performed in [9]. It is also assumed in [8] that the Gd ions in positions (0, 0, ±z) are non equivalent, and the magnetic moments at these ions are irregular in magnitude.…”

“…The magnetoelectric effect in the Gd 2 CuO 4 com pound was studied in [9].The possibility of existence of the magnetoelectric effect is thought to be related to the fact that the antiferromagnetic ordering of copper spins leads to doubling the crystal lattice, conserving the system symmetry with respect to space inversion. By contrast, the ferromagnetic planes of the rare earth spins, being coupled antiferromagnetically, violate the symmetry with respect to space inversion but do not influence the translation symmetry.…”

“…By contrast, the ferromagnetic planes of the rare earth spins, being coupled antiferromagnetically, violate the symmetry with respect to space inversion but do not influence the translation symmetry. In [9], when ana lyzing the magnetoelectric effect, it was supposed that the compound belongs to the orthorhombic class mm'm. This magnetic class allows the existence of the magnetoelectric effect and is characterized by two independent components of the magnetoelectric ten sor.…”

Fe – Ga ∕ Pb ( Mg 1 ∕ 3 Nb 2 ∕ 3 ) O 3 – Pb Ti O 3 magnetoelectric laminate composites

“…ME effects have been found in many two-phase composites of magnetostrictive materials, such as Tb 1−x Dy x Fe 2−y , Permendur, Ni 1−x Co x Fe 2 O 4 ͑i.e., NFO͒, or Co 1−x Zn x Fe 2 O 4 ͑i.e., CFO͒, and piezoelectric materials, such as Pb͑Zr, Ti͒O 3 or PMN-PT layers. [10][11][12][13][14][15][16][17][18][19][20][21] In our prior article, we reported the magnetostrictive and magnetoelectric behavior of Fe-20 at. % Ga/ Pb͑Zr, Ti͒O 3 laminates.…”