Abstract:The bulk magnetic properties of the new quasi-one-dimensional Heisenberg antiferromagnet, CuCrO4, were characterized by magnetic susceptibility, heat capacity, optical spectroscopy, EPR and dielectric capacitance measurements and density functional evaluations of the intra-and inter-chain spin exchange interactions. We found type-II multiferroicity below the Néel temperature of 8.2(5) K, arising from competing antiferromagnetic nearest-neighbor (Jnn) and next-nearest-neighbor (Jnnn) intra-chain spin exchange i… Show more
“…The feature at high T (upturn below 100 K) may arise due to the presence of AFM couplings (short-range correlation above ordering). Similar upturn in the ε′ ( T ) has also been observed in many multiferroic and/or magneto-electric oxides due to magnetic correlations 18–20 . Though, we did not observe any signature of ferroelectricity by pyoelectric measurement within the resolution limit of our instrument.Figure 2χ( T ) measured in 0.5 T. The solid line is a fit to 1/χ data, while the dashed line represents the extrapolation.…”
We report the magnetic and dielectric behavior of Pb6Ni9(TeO6)5, a new compound comprising the honeycomb-like layers of S = 1 spins, through detailed structural, magnetic and dielectric investigation. An antiferromagnetic-type transition at 25 K (T
N) with weak-ferromagnetic behavior is revealed. Interestingly, a large value of coercive field of 1.32 T at 2 K is observed. The isothermal magnetization after zero-field-cooled condition, it exhibits the presence of large spontaneous exchange bias (SEB) with a magnitude of 0.19 T at 2 K; which is rare in single bulk materials, especially without external doping. The value of |H
EB| further enhances to 0.24 T under 16 T field-cooled condition, confirming the presence of large exchange bias in the material.
“…The feature at high T (upturn below 100 K) may arise due to the presence of AFM couplings (short-range correlation above ordering). Similar upturn in the ε′ ( T ) has also been observed in many multiferroic and/or magneto-electric oxides due to magnetic correlations 18–20 . Though, we did not observe any signature of ferroelectricity by pyoelectric measurement within the resolution limit of our instrument.Figure 2χ( T ) measured in 0.5 T. The solid line is a fit to 1/χ data, while the dashed line represents the extrapolation.…”
We report the magnetic and dielectric behavior of Pb6Ni9(TeO6)5, a new compound comprising the honeycomb-like layers of S = 1 spins, through detailed structural, magnetic and dielectric investigation. An antiferromagnetic-type transition at 25 K (T
N) with weak-ferromagnetic behavior is revealed. Interestingly, a large value of coercive field of 1.32 T at 2 K is observed. The isothermal magnetization after zero-field-cooled condition, it exhibits the presence of large spontaneous exchange bias (SEB) with a magnitude of 0.19 T at 2 K; which is rare in single bulk materials, especially without external doping. The value of |H
EB| further enhances to 0.24 T under 16 T field-cooled condition, confirming the presence of large exchange bias in the material.
“…In such compounds it is frequently found that the spin exchange interactions between the Cu 2+ (S=1/2) ions are such that the next-nearest-neighbor (NNN) exchange is antiferromagnetic (AFM), the nearest-neighbor (NN) exchange is ferromagnetic (FM), and the NNN spin exchange is often considerably stronger than the NN spin exchange. Due to the inherent competition of the NN and NNN spin exchange interactions, the CuX 2 ribbon chains tend to develop unusual AFM incommensurate spiral spin structures [1][2][3][4][5][6][7][8][9] and sometimes concomitantly multiferroic behavior. [10][11][12][13] These CuX 2 ribbon chains are formed by linking CuX 4 basal-square-planes of axially elongated CuX 6 (X = O, Cl, Br,...) octahedra together via their trans-edges.…”
The magnetic and lattice properties of the S=1/2 quantum-spin-chain ferromagnet, CuAs2O4, mineral name trippkeite, were investigated. The crystal structure of CuAs2O4 is characterized by the presence of corrugated CuO2 ribbon chains. Measurements of the magnetic susceptibility, heat capacity, electron paramagnetic resonance and Raman spectroscopy were performed. Our experiments conclusively show that a ferromagnetic transition occurs at ∼7.4 K. Ab initio DFT calculations reveal dominant ferromagnetic nearest-neighbor and weaker antiferromagnetic nextnearest-neighbor spin exchange interactions along the ribbon chains. The ratio of Jnn/Jnnn is near -4, placing CuAs2O4 in close proximity to a quantum critical point in the Jnn -Jnnn phase diagram. TMRG simulations used to analyze the magnetic susceptibility confirm this ratio. Single-crystal magnetization measurements indicate that a magnetic anisotropy forces the Cu 2+ spins to lie in an easy plane perpendicular to the c-axis. An analysis of the field and temperature dependent magnetization by modified Arrott plots reveals a 3d-XY critical behavior. Lattice perturbations induced by quasi-hydrostatic pressure and temperature were mapped via magnetization and Raman spectroscopy.
“…Here, we are dealing with an insulator, in which the asymmetry arises from the influence of non-diagonal elements of the dynamic susceptibility. This effect is often observed in systems with interactions of low symmetry, geometrical frustration and sufficiently broad resonance lines (B r B) [46][47][48][49].…”
We present a comprehensive experimental and theoretical study of the electronic and magnetic properties of two quasi-two-dimensional (2D) honeycomb-lattice monoclinic compounds A 3 Ni 2 SbO 6 (A=Li, Na). Magnetic susceptibility and specific heat data are consistent with the onset of antiferromagnetic (AFM) long range order at low temperatures with Néel temperatures ~ 14 and 16 K for Li 3 Ni 2 SbO 6 and Na 3 Ni 2 SbO 6 , respectively. The effective magnetic moments of 4.3 B /f.u. (Li 3 Ni 2 SbO 6 ) and 4.4 B /f.u. (Na 3 Ni 2 SbO 6 ) indicate that Ni 2+ is in a high-spin configuration (S=1). The temperature dependence of the inverse magnetic susceptibility follows the Curie-Weiss law in the high-temperature region and shows positive values of the Weiss temperature ~ 8 K (Li 3 Ni 2 SbO 6 ) and ~12 K (Na 3 Ni 2 SbO 6 ) pointing to the presence of nonnegligible ferromagnetic interactions, although the system orders AFM at low temperatures. In addition, the magnetization curves reveal a field-induced (spin-flop type) transition below T N that can be related to the magnetocrystalline anisotropy in these systems. These observations are in agreement with density functional theory calculations, which show that both antiferromagnetic and ferromagnetic intralayer spin exchange couplings between Ni 2+ ions are present in the honeycomb planes supporting a zigzag antiferromagnetic ground state. Based on our experimental measurements and theoretical calculations we propose magnetic phase diagrams for the two compounds. 75.30.Kz; 75.10.Dg; 75.30.Gw; 75.30.Et
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