Novel spin lattice in Cu₃TeO₆: an antiferromagnetic order and domain dynamics

Abstract

We report on the magnetic properties of an insulating cubic compound Cu3TeO6 studied by ac and dc susceptibility, torque magnetometry and neutron powder diffraction. A novel three-dimensional magnetic lattice composed of almost planar regular hexagons of Cu2+ S = 1/2 spins is present in Cu3TeO6. The magnetic susceptibility in the paramagnetic state obeys the Curie–Weiss law in the 200–330 K regime with ΘCW = −148 K and at TN = 61 K system undergoes an antiferromagnetic phase transition. Above TN the susceptibility is isotropic. Below TN a large anisotropy develops in fields H≥500 Oe. Torque measurements reveal the presence of antiferromagnetic domains below TN. In a rather low magnetic field ( Oe) switching of domains is observed. The dynamics related to movement of domain walls is very slow at low temperatures (of the order of 102 s) and interferes with all torque measurements. The presence of domains is a consequence of the symmetry of the underlying magnetic lattice. Neutron powder diffraction reveals that antiferromagnetic long-range order is associated with the wavevector . The dominant component of the magnetic moment is along one of the space diagonals of the cubic unit cell, but it is not possible to resolve whether the structure is collinear or canted.

Synthesis and Structural Determination of the Disordered Bixbyite Cu3‐xSb1+xO5.5+3x/2 with Spin‐Glass Behaviour

“…As of the last decade, the copper tellurate Cu 3 TeO 6 with a bixbyite structure a= 9.537 Å has been the focus of intense studies due to its unique magnetic spin‐web structure driven by the ordering of spin of 3d 9 copper and the proof of topological magnons for the first time in a 3D antiferromagnet . The nearest neighbour copper ions (≈3.18 Å) form a 3D network of 8 corner sharing hexagons centered around Te 6+ in the lattice.…”

“…All adjacent hexagons are oriented differently in space which results in 4 unique AFM domains below T c =61 K. When taking into account exchange with the second nearest neighbours (≈3.6 Å) a frustrated triangular sub‐lattice is formed which forms a pseudo‐Kagome type lattice that could prevent AFM ordering. Studies concluded that this exchange interaction must be significantly weaker than the nearest neighbour exchange and should only produce a slight tilting of the spin orientation . Inelastic neutron scattering studies showed that super‐super exchange (Cu‐O‐O‐Cu) through the 9 th nearest neighbour contributed significantly to the stability of the magnetic structure with an exchange energy comparable to the first nearest neighbour exchange .…”

“…Two FM‐coupled layers are out of plane from each other, magnetic moments of this given AFM domain are aligned perpendicular to the plane. Magnetic moment vectors shown are arbitrary in size …”

“…Inelastic neutron scattering studies showed that super‐super exchange (Cu‐O‐O‐Cu) through the 9 th nearest neighbour contributed significantly to the stability of the magnetic structure with an exchange energy comparable to the first nearest neighbour exchange . It was postulated that if the spin tilt was not present, the unit cell would distort away from the cubic system due to the resultant magneto‐elastic strain . Raman experiments have provided evidence of a magnetically driven phase transition occurring below the AFM transition temperature with the appearance of a new phonon mode …”

Structural and magnetic dimers in the spin-gapped systemCuTe2O5

“…in CuGeO 3 below the spinPeierls transition. 11 Therefore, we will concentrate in the following on the temperature regime above 20 K. In the investigated temperature regime the g values are practically temperature independent with g a * = 2.27(2), g b = 2.11 (3), and g c = 2.10(2), where a * denotes the direction perpendicular to the b-c plane. Such g values slightly enhanced with respect to the spin-only value of g = 2 are typical for the 3d 9 electronic configuration of Cu 2+ in distorted oxygen octahedra, where the orbital momentum is nearly quenched by the crystal field.…”