Magnetic phase diagram of the two-dimensional antiferromagnetNi5(TeO3)4Br<

Abstract

Phase diagram of the two-dimensional antiferromagnet Ni 5 ͑TeO 3 ͒ 4 Br 2 with triangular arrangement of Ni 2+ ͑S =1͒ magnetic moments within the ͓Ni 5 O 17 Br 2 ͔ subunits has been investigated by temperature and magnetic field dependent heat-capacity, magnetization, and magnetic-torque measurements down to 1.5 K and up to 23 T. A nonzero magnetic contribution to the heat capacity observed up to 2.3T N is consistent with short-range magnetic ordering and the two-dimensional nature of the system. Below the Néel temperature T N =29 K several antiferromagnetic phases were identified. The zero-field phase is characterized by a planar antiferromagnetic arrangement of the two in-layer neighboring ͓Ni 5 O 17 Br 2 ͔ magnetic clusters within the magnetic unit cell. When the magnetic field is applied along the a ‫ء‬ crystal axis, a spin-flop-like transition to a phase with a complex out-of-plane arrangement of Ni 2+ ͑S =1͒ magnetic moments occurs at ϳ10 T. Using a molecular-field approach we predict that this transition will shift to higher fields with increasing temperature and that a magnetic phase with ferromagnetic ordering of ͓Ni 5 O 17 Br 2 ͔ magnetic clusters will occur above 24 T. We ascribe the richness of the magnetic phases to strongly exchange-coupled clusters, being the basic building blocks of the investigated layered system.

High-field magnetization of a two-dimensional spin frustration system, Ni5(TeO3)4X2(X = Br, Cl)

“…A step-like transition was observed at 11 T(10 T) for X = Br(Cl), which was consistent with other study by ESR spectroscopy or magnetization measurements. At around 24 T, we did not observe any sign of another transition, which was inconsistent with the prediction by Pregelj's report [10]. From M(H) curves, we found that ∆M per formula is close to one half of m N i .…”

Functionally Gradient Material Ceramics of Hydroxyapatite and Yttria Partially Stabilized Zirconia Prepared by Spark Plasma Sintering for Biocompatibility and Mechanical Strength

“…A step-like transition was observed at 11 T (10 T) for X = Br (Cl), which was consistent with other studies using ESR spectroscopy or magnetization measurements. At around 24 T, we did not observe any sign of another transition, which was inconsistent with the prediction by Pregelj's report [10]. From M(H ) curves, we found that M per formula is close to one half of m Ni .…”

“…In the present study, we focus on the field-dependent magnetization of these compounds using a pulse magnet which generates magnetic fields up to 55 T. A step-like transition, at around 11 T (10 T) for X = Br (Cl), was observed in the M(H ) curves, which is consistent with Pregelj's results and also with ESR experiments [6,9,10]. Interestingly, there is no signature of another field-induced transition up to 55 T. However, as the M(H ) curves showed unsaturated behavior up to the highest field in the current measurements, there exists the possibility of a second transition occurring at fields higher than 55 T.…”

“…The absolute values of the magnetization curves are carefully calibrated by means of low-field magnetization measurements which were performed using a SQUID magnetometer (Quantum Design MPMS). [6,9], and also the previous field-dependent magnetization data [10].…”

“…The high-field magnetization measurements can provide more information of high-field state of these samples. Very recently, Pregelj et al reported a magnetization study of Ni 5 (TeO 3 ) 4 Br 2 in magnetic fields up to 12 T. A transition peak was observed in the dM/dH curve at ∼11 T, which is suggested to be related to the spin-flop-like transition in ESR experiments [10]. A model, including spin-ion anisotropy, was proposed to explain this observation.…”