Successive Magnetic-Field-Induced Transitions and Colossal Magnetoelectric Effect inNi3TeO6

Abstract

We report the discovery of a metamagnetic phase transition in a polar antiferromagnet Ni 3 TeO 6 that occurs at 52 T. The new phase transition accompanies a colossal magnetoelectric effect, with a magneticfield-induced polarization change of 0.3 μC=cm 2 , a value that is 4 times larger than for the spin-flop transition at 9 T in the same material, and also comparable to the largest magnetically induced polarization changes observed to date. Via density-functional calculations we construct a full microscopic model that describes the data. We model the spin structures in all fields and clarify the physics behind the 52 T transition. The high-field transition involves a competition between multiple different exchange interactions which drives the polarization change through the exchange-striction mechanism. The resultant spin structure is rather counterintuitive and complex, thus providing new insights on design principles for materials with strong magnetoelectric coupling. Magnetoelectric (ME) multiferroics have been extensively studied recently to understand the mechanisms responsible for cross-coupling between magnetism and ferroelectricity, which is at the heart of their promise for applications in multifunctional devices [1][2][3][4][5][6]. In this class of materials, at least three mechanisms are known to induce ferroelectric polarization (P) upon magnetic order: (1) the spin current or inverse Dzyaloshinskii-Moriya (DM) interaction in a spin-cycloidal structure which is mediated by antisymmetric exchange [7][8][9], (2) the symmetric exchange-striction mechanism in collinear magnets [10], and (3) the hybridization between metal d and ligand p orbitals that is modulated by spin direction [11]. A majority of ME couplings that have been studied to date involve mechanisms (1) and (3). However, the symmetric exchange mechanism (2) can, in principle, also lead to large ME effects.Another route to a large ME effect is to consider magnetic systems that have a polar structure. This condition meets the prerequisites for the ME effect; i.e., the coexistence of broken spatial-inversion symmetry and timereversal symmetry. Often, these systems exhibit a nonpolar to polar structural transition at high temperatures and magnetic ordering at lower temperatures. A well-known example is BiFeO 3 , with ferroelectric and antiferromagnetic transition temperatures at 1100 K and 653 K, respectively [12]. However, its ME effect is small compared to those of spin-driven ME materials.Recently, a ME effect has been observed in the corundum-related compound Ni 3 TeO 6 (NTO). It crystallizes in a polar R3 space group with three Ni 2þ ions (3d 8 , S ¼ 1) and a nonmagnetic Te ion arranged along the c axis in a unit cell [ Fig. 1(a)] to form a linear chain with broken spatialinversion symmetry. This material is not ferroelectric but pyroelectric; i.e., the electric polarization cannot be switched by an external electric field. However, in addition to its nonswitchable electric polarization component due to the polar structure, it also shows a...

H−T phase diagram of solid oxygen

“…The thermodynamical α-θ transition field is obtained at around 90 T. Recently, such an ultrahigh magnetic field becomes accessible using non-destructive pulse magnets and applied to the researches in condensed matter physics [19][20][21][22]. If the magnetic field is generated for few ms, H max = 100 T might be enough to observe the θ phase since hysteresis becomes smaller.…”

Magnetoelectric Coupling through the Spin Flop Transition inNi3TeO6

“…Moreover, Ni 3 TeO 6 sports the largest linear magnetoelectric coupling constant in a single-phase material known to date (α = 1, 300 ps/m) [13]. Metamagnetic transitions accompanied by extraordinarily large polarization changes have been discovered at 52 and 70 T [15], and indications of an unexplored transition between 30 and 35 T were observed as well [16]. The colossal polarization, rich magnetic phase diagram, and large spin-orbit coupling due to incorporation of the Te centers raise the possibility of large dynamic magnetoelectric coupling in this system.…”

“…Recent magnetization and magneto-infrared experiments do in fact reveal the possibility of an unexplored transition between 30 and 35 T as well as metamagnetic transitions at 52 and 70 T for B c [15,16].…”

Magnetic field-temperature phase diagram of multiferroic [(CH3)2NH2]Mn(HCOO)3<

“…Examples include the classic spin flop, 1-6 magnetic saturation transitions, [7][8][9] and those with a sequence of metamagnetic, helical, and nano-pantograph spin states. [10][11][12] The emergent class of tunable multiferroics with chemical formula [(CH 3 ) 2 NH 2 ]M (HCOO) 3 (M = Mn 2+ , Fe 2+ , Ni 2+ , Co 2+ ) provides a number of exciting opportunities in this regard. The Mn analog [(CH 3 ) 2 NH 2 ]Mn(HCOO) 3 is ferroelectric below T C =185 K with polarization P =1.5 µC/cm 2 .…”