Canted Antiferromagnetic Transition Research Articles

Chemical pressure effects on Tm1-yRyMn0.3Co0.7O3 due to element substitution at A-site

To clarify the chemical pressure effects on TmMn0.3Co0.7O3 due to element substitution at an A-site, the crystal structure and magnetic properties of Tm1-yRyMn0.3Co0.7O3 (R = Y and Lu) were investigated. All the prepared samples possessed a perovskite-type orthorhombic structure with the Pnma space group, and the unit-cell volume V increased with the average radius of A-site ions 〈rR〉. From the effective magnetic moment Peff and M−H measurements, it was found that the electronic states of the ions in the samples were Tm3+, Mn4+, Co2+(high-spin state, S = 3/2), and Co3+(low-spin state, S = 0). The physical parameters including the canted antiferromagnetic transition temperature Tc increased with V. The field-cooled magnetization MFC below 30 K could be explained by the antiferromagnetic interaction between the paramagnetic Tm and the 3d metal sublattices. Since Tc and the fitting parameter of this two-sublattice model increased with V, these changes were considered to be attributed to the chemical pressure generated by element substitution at the A-site.

Characterization of V2O3 Nanoscale Thin Films Prepared by DC Magnetron Sputtering Technique

Vanadium sesquioxide V2O3, a transition metal oxide, is an important metal transition insulator due to its potential applications in novel electronic and memory devices. V2O3 thin films of thickness around 230 nm were grown on Si/SiO2/Ti/Pt substrates at deposition temperature of 723 K in a controlled Ar:O2 atmosphere of 35:2.5 sccm employing Direct Current (DC) magnetron sputtering. X-ray diffraction studies confirmed single phase of the material stabilized in corundum rhombohedral R3¯C phase. X-ray photoelectron spectroscopic results revealed chemical oxidation states are of V3+ and O2− and have nearly stochiometric elemental compositions in the films. Magnetization studies down to 10 K predicts a canted antiferromagnetic transition around 55 K. Out of 7 expected Raman active modes (2A1g + 5Eg), two A1g Raman active modes at 242 and 500 cm−1 were observed at ambient R3¯C phase. Temperature dependent Raman spectroscopic studies carried out from 80 to 300 K identified a monoclinic to rhombohedral phase transition at ~143 K.

Significance of isostructural distortion and strong magnetoelastic coupling in the weak ferromagnet YFe0.9Cr0.1O3

We report the appearance of weak ferromagnetism above the long-range canted antiferromagnetic order TN = 553 K at which the Fe-Cr interactions become dominant in YFe0.9Cr0.1O3. The weak ferromagnetic order above TN appears due to the increasing magnetic interactions in Fe-sublattices resulting in a canted antiferromagnetic transition at TFe-Fe = 620 K. Electrical hysteresis loop studies and Positive-Up Negative-Down protocol measurements reveal spontaneous but weak ferroelectricity in the system. Dielectric measurements as a function of temperature and frequency reveal a relaxorlike dielectric anomaly within a temperature interval of 400–500 K and anomalous signatures at and temperatures above TN. Synchrotron x-ray diffraction studies over a broad temperature range, 298–873 K, illustrate a significant magnetoelastic coupling at TN and around TFe-Fe. Isostructural distortions are further revealed over the temperature range of 400–500 K from the x-ray diffraction studies. Analyses of the diffraction patterns reveal the delicate interplay between the in-plane and out-of-plane exchange interactions over TN and in isostructural distortion regions. We strongly argue that the ferroelectricity in YFe0.9Cr0.1O3 results from the magnetostriction and Dzyaloshinskii-Moriya interaction manifested through a significant magnetoelastic coupling at TN and TFe-Fe.

Magnetic diversity in three-dimensional two-fold-interpenetrated structures: a story of two compounds.

A magnetostructural correlation has been carried out for two newly synthesized two-fold-interpenetrated three-dimensional structures. Compound 1, denoted as [Ni(L1)(L2)]·2DMF (where L1 is 1,4-benzene-dicarboxylic acid (BDC), L2 is 4,4-oxybis-(N-(pyridine-4-yl)benzamide), and DMF is N,N'-dimethylformamide), was observed to have a three-dimensional structure with two-fold interpenetration. Compound 2, denoted as [Co(L3)(L2)]·2DMF (where L3 is 2,5-thiopehene-dicarboxylic acid (TDC)), was also observed to display a three-dimensional structure with an architecture identical to that of compound 1. Both compounds were well characterised using several techniques including single-crystal X-ray diffraction, powder X-ray diffraction, TGA, and IR. Magnetism and specific heat measurements of compound 1 revealed a canted-antiferromagnetic transition at TN ≈ 4 K and a field-induced spin-flop transition at a relatively low field strength. These exotic features were attributed to the low-symmetry space group P(1[combining macron]) and single-ion anisotropy of the Ni2+ sub-lattice. In contrast, compound 2 was found to be weakly antiferromagnetic in nature with a negligible interaction between the magnetic Co2+ ions.

Magnetization switching of rare earth orthochromite CeCrO3

We report the synthesis of single phase rare earth orthochromite CeCrO3 and its magnetic properties. A canted antiferromagnetic transition with thermal hysteresis at T = 260 K is observed, and a magnetic compensation (zero magnetization) near 133 K is attributed to the antiparallel coupling between Ce3+ and Cr3+ moments. At low temperature, field induced magnetization reversal starting from 43 K for H = 1.2 kOe reveals the spin flip driven by Zeeman energy between the net moments and the applied field. These findings may find potential uses in magnetic switching devices such as nonvolatile magnetic memory which facilitates two distinct states of magnetization.

Giant zero field cooled spontaneous exchange bias effect in phase separated La1.5Sr0.5CoMnO6

We report a giant zero field cooled exchange bias (ZEB) effect (∼0.65 T) in La1.5Sr0.5CoMnO6 sample. Magnetic study has revealed a reentrant spin glass ∼90 K, phase separation to spin glass and ferromagnetic phases below 50 K and canted antiferromagnetic transition ∼10 K. A small conventional exchange bias (CEB) is established with the advent of spontaneous phase separation down to 10 K. Giant ZEB and enhanced CEB effects are found only below 10 K and are attributed to the large unidirectional anisotropy at the interface of isothermally field induced ferromagnetic phase and canted antiferromagnetic background.

Phase diagrams of strained Ca1–xCexMnO3 films

The transport and magnetic properties were examined of thin films of the electron-doped manganite Ca1−xCexMnO3 (CCMO; 0 ≤ x ≤ 0.1) deposited on three different single-crystalline oxide substrates: YAlO3, NdAlO3, and LaSrAlO4, which subject the films to a compressive strain, a practical lattice matching, and a tensile strain, respectively. The temperature dependence of the activation energy extracted from the resistivity–temperature curves clearly indicated the phase transitions in the CCMO films. A comparison with magnetization measurements revealed that regardless of the substrates, the temperature-driven phase transition of the CCMO films changed from the G-type antiferromagnetic transition at x = 0 to the canted antiferromagnetic transition and to the charge- and/or orbital-ordered transition, as x was increased. In the canted antiferromagnetic phase, the epitaxial strains have significant impact not only on the transport properties but also on the magnetic properties such as the spontaneous magnetization and the magnetic anisotropy, confirming that the competition between antiferromagnetic super-exchange and ferromagnetic double-exchange interactions results in the canted antiferromagnetic state in the electron-doped CCMO films. Based on the results of the transport and magnetic measurements, the temperature versus band-filling phase diagrams of the strained CCMO films on three different substrates were established.

High-pressure stability relations, crystal structures, and physical properties of perovskite and post-perovskite of NaNiF3

NaNiF3 perovskite was found to transform to post-perovskite at 16–18GPa and 1273–1473K. The equilibrium transition boundary is expressed as P (GPa)=−2.0+0.014×T (K). Structure refinements indicated that NaNiF3 perovskite and post-perovskite have almost regular NiF6 octahedra consistent with absence of the first-order Jahn–Teller active ions. Both NaNiF3 perovskite and post-perovskite are insulators. The perovskite underwent a canted antiferromagnetic transition at 156K, and the post-perovskite antiferromagnetic transition at 22K. Magnetic exchange interaction of NaNiF3 post-perovskite is smaller than that of perovskite, reflecting larger distortion of Ni–F–Ni network and lower dimension of octahedral arrangement in post-perovskite than those in perovskite.

Bixbyite-Type V2O3—A Metastable Polymorph of Vanadium Sesquioxide

A metastable polymorph of vanadium sesquioxide was prepared by the reaction of vanadium trifluoride with a water-saturated gaseous mixture of 10 vol % hydrogen in argon. The new polymorph crystallizes in the bixbyite-type structure. At temperatures around 823 K a transformation to the well-known corundum-type phase is observed. Quantum-chemical calculations show that the bixbyite-type structure is about 9 kJ/mol less stable than the known corundum-based one. This result, in combination with the absence of imaginary modes in the phonon density of states, supports the classification of the bixbyite-type phase as a metastable V(2)O(3) polymorph. At ~50 K a paramagnetic to canted antiferromagnetic transition is detected.

Ferromagnetic Enhancement of CE-Type Spin Ordering in(Pr,Ca)MnO3

We present resonant soft x-ray scattering results from small bandwidth manganites (Pr,Ca)MnO(3), which show that the CE-type spin ordering (SO) at the phase boundary is stabilized only below the canted antiferromagnetic transition temperature and enhanced by ferromagnetism in the macroscopically insulating state (FM-I). Our results reveal the fragility of the CE-type ordering that underpins the colossal magnetoresistance effect in this system, as well as an unexpected cooperative interplay between FM-I and CE-type SO which is in contrast to the competitive interplay between the ferromagnetic metallic state and CE-type ordering.

Magnetoelectric properties of (Ca1−xSrx)2CoSi2O7 Crystals

We have investigated the magnetoelectric properties of (Ca1−xSrx)2CoSi2O7 (0 ≤ x ≤ 1) crystals with a quasi-two-dimensional structure. In Ca2CoSi2O7 (x = 0), a canted antiferromagnetic transition occurs at 5.6 K. The transition temperature TN is increasing with increasing Sr concentration, and the rises of the magnetization and dielectric constant become larger. Since the dielectric constant shows large change at TN and the magnetocapacitance effect is observed below TN, a coupling between the magnetism and dielectricity is strong in (Ca1−xSrx)2CoSi2O7. The positive magnetocapacitance is reduced by Sr substitution, and is not observed in x ≥ 0.5. Namely, the compound of x ≥ 0.5 does not show the magnetic-field-induced electric polarization. On the other hand, the negative magnetocapacitance is enhanced by Sr substitution.

Multiple magnetic transitions in multiferroicBiMnO3

The magnetic phase variations under hydrostatic pressure on multiferroic BiMnO3 have been examined by the dc magnetization [Mg(T)], magnetic hysteresis [Ueff(H)], and ac susceptibility [X'g(T)]. Three magnetic transitions, manifested as kinks I, II, and III on the Mg(T)], curves, were identified at 8.7 and 9.4 kbar. With increasing pressure, transition temperatures of kink I and kink II TkI and TkII tend to decrease, but the temperature of kink III TkIII showed more complex variation. Under increasing magnetic field, TkI and TkII increase; however, TkIII decreases. Combining [Mg(T)] curves with Ueff(H) and X'g(T), more detailed properties of these three kinks would be shown as follows. Kink I is a long-range soft ferromagnetic transition which occurs at TkI 100 K under ambient pressure but is suppressed completely at 11.9 kbar. Kink II emerges at 8.7 kbar along with TkII 93 K which is also long-range soft ferromagnetic but canted in nature. Kink III, a canted antiferromagnetic transition, appears at TkIII 72.5 K along with kink II also at 8.7 kbar. The proposed phase diagrams at ambient pressure, 9.4 and 11.9 kbar show the different magnetic features of BiMnO3. These findings are believed to result from the variations in crystal structure influenced by the external pressure. These results also indicate the common complicated

Gigantic magnetoelectric effect caused by magnetic-field-induced canted antiferromagnetic-paramagnetic transition in quasi-two-dimensional Ca2CoSi2O7 crystal

We have investigated the magnetic and dielectric properties of Ca2CoSi2O7 crystal. The dielectricity and magnetism of Ca2CoSi2O7 are strongly coupled below a canted antiferromagnetic transition temperature (TN). Magnetic fields induce electric polarization below TN. Interestingly, the magnetic-field-induced electric polarization is detected even without poling electric fields. Below TN, a canted antiferromagnetic-paramagnetic transition is induced by magnetic fields. The large magnetocapacitance is observed around TN. The origin of the large magnetocapacitance is due to the magnetic-field-induced the canted antiferromagnetic-paramagnetic transition.

Insulator to metal transition induced by substitution in the nearly two‐dimensional compound CuCr 1– x V x S 2

CuCrS2 has a nearly two-dimensional crystal structure, and is an insulator with antiferromagnetic ordering at T N = 40 K. We have prepared the substituted system described as CuCr1-x Vx S2. Powder x-ray diffraction patterns reveal that this system has a large solubility range of 0 ≤ x ≤ 0.9, within which single-phased sample is obtained. Electrical conductivity was almost insulating for x < 0.3, which turns to metallic for x ≈ 0.9. Thus, insulator-metal transition induced by substitution occurs around x = 0.8. Magnetic susceptibility measurements show weak ferromagnetic behavior below T = 30 K for x > 0, which is likely to be a canted-antiferromagnetic transition. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Magnetic susceptibility of a two phase manganite Pr0.925Na0.075MnO3

Abstract Magnetic measurements on the Pr 0.925 Na 0.075 MnO 3 polycrystalline manganite were performed with the aim to investigate the coexistence of the canted antiferromagnetic (CAF) and ferromagnetic (FM) phases proved by the neutron diffraction. The AC susceptibility χ ( H , T ) and the remanent magnetization M r ( T ) seem to be correlated with the FM to CAF transition temperature. The frequency dependence of χ ( H , T ) suggests a disorder character (spin-glass like) of this two phase system.

Electron Spin Resonance in Pr0.65Ca0.35MnO3

The magnetic behavior of the distorted perovskite manganese, Pr0.65Ca0.35MnO3 was studied by X-band electron spin resonance for powder samples. We observed the onset of the charge-ordered state at TCO∼215 K, the antiferromagnetic transition with the peak of the ESR linewidth, ΔHp−p at TAF∼180 K and the canted antiferromagnetic transition at TCAF∼125 K associated with the abrupt increase of both the effective magnetization and ΔHp−p. Below 90 K, the absorption intensity profile becomes weakened with decreasing temperature suggesting the existence of some kind of magnetic disorder below 90 K, which is responsible for a part of evidence of the existence of the spin-glass state as has been proposed by Yoshizawa et al., Phys. Rev. B52, 1689 (1996).