Electric field modulation of the tetragonal domain orientation revealed in the magnetic ground state of quantum paraelectric EuTiO3

Abstract

We present a study of the thermodynamic and magnetic properties of single-crystal EuTiO3. Signatures of metastability are visible in the heat capacity below the cubic-tetragonal phase transition at 283 K, supporting the evidence for a mismatch between long and short range structural order from previous X-ray diffraction studies. Employing the anisotropic magnetization as an indirect structural probe, we confirm the emergence of multiple orthogonal domains at low temperature. Torque magnetometry is capable of revealing the nature and temperature-dependence of the magnetic anisotropy in spite of the domain misalignment; we hence deduce that tetragonal EuTiO3 enters an easy-axis antiferromagnetic phase at 5.6 K, with a first-order phase transition to an easyplane ground state below 3 K. Our experimentally-determined magnetic phase diagram is accurately reproduced by a 3D anisotropic Heisenberg spin model. Furthermore, we demonstrate that electric field cooling acts to suppress this orientational disorder by realigning the domains, due to the strong coupling between electric fields and lattice dipoles characteristic of paraelectric materials.

EuTiO3magnetic structure studied by neutron powder diffraction and resonant x-ray scattering

“…Therefore, our diffraction measurements suggests that in the unpoled sample the magnetic moments stay within the a,b plane, even above T * . In this respect, results from Petrovic et al 65 suggest an appealing possibility to manipulate the Eu spins through an applied external electric field.…”

“…Finally, we comment on recent experiments that have proposed the existence of another critical temperature T * = 2.75 K. 65 It is suggested that above this temperature the magnetic moment easy axis flops from the a,b plane to the c axis. The existence of such a phase has been revealed by poling the sample under electric field, which effectively creates a monodomain sample.…”

“…Whereas if we were to postulate that the moments were along the [100] direction (see the dotted line in Fig. 4 65 The proposed motif for the magnetic moments is illustrated in Fig. 5.…”

Nonlinear pressure dependence ofTNin almost multiferroic EuTiO3

“…Since the data have been taken at low temperatures, ETO is in the tetragonal phase. However, with the tetragonal distortion being very small [12,13,26], the pseudocubic lattice constant is used and plotted as a function of pressure. This shrinks linearly with pressure.…”

“…It is also important to mention in this context that in quasi-two-dimensional (2D) materials their physics is very different from that observed for their three-dimensional (3D) analogues, which makes it impossible to discuss phenomena observed in these 2D compounds in relation to the bulk materials. The low temperature phase has already been addressed experimentally via different approaches [12,13], namely by investigating its magnetic and electric field dependences. From these studies it is concluded that the ground state of ETO is a multidomain state with the possibility of developing ferroelectricity if symmetry breaking can be achieved.…”