Magnetic and Transport Properties of PrNi Single Crystal

Frequency dependence of χ (T ), different position of a maximum in χ (T ) for different crystal orientations, hysteretic behavior between magnetization measurements in zero-field cooling and field coolding regime are attributed to strong magneto-crystalline anisotropy of PrNi ferromagnetic single crystal with T C = 20.5 K, which is driven by crystal field effect. Applied pressure shifts T C to higher temperatures (dT C /dp = 1 K/GPa). Susceptibility follows the Curie-Weiss law except for b-axis, which is hard magnetic axis. An anisotropic behavior was seen in resistivity measurements with the largest difference between b-axis and c-axis. Resistivity below TC can be described by power law with ρ ∼ T 2.24 and is field dependent with a positive magnetoresistance

Strain relaxation dynamics of multiferroic orthorhombic manganites

Abstract: Resonant ultrasound spectroscopy has been used to characterise strain coupling and relaxation behavior associated with magnetic/magnetoelectric phase transitions in GdMnO3, TbMnO3 and TbMn0.98Fe0.02O3 through their influence on elastic/anelastic properties. Acoustic attenuation ahead of the paramagnetic to colinear-sinusoidal incommensurate antiferromagnetic transition at ∼41 K correlates with anomalies in dielectric properties and is interpreted in terms of Debye-like freezing processes. A loss peak at ∼150 K is related to a steep increase in electrical conductivity with a polaron mechanism. The activation energy, E a, of ≳0.04 eV from a loss peak at ∼80 K is consistent with the existence of a well-defined temperature interval in which the paramagnetic structure is stabilised by local, dynamic correlations of electric and magnetic polarisation that couple with strain and have relaxation times in the vicinity of ∼10−6 s. Comparison with previously published data for Sm0.6Y0.4MnO3 confirms that this pattern may be typical for multiferroic orthorhombic RMnO3 perovskites (R = Gd, Tb, Dy). A frequency-dependent loss peak near 10 K observed for TbMnO3 and TbMn0.98Fe0.02O3, but not for GdMnO3, yielded E a ⩾ ∼0.002 eV and is interpreted as freezing of some magnetoelastic component of the cycloid structure. Small anomalies in elastic properties associated with the incommensurate and cycloidal magnetic transitions confirm results from thermal expansion data that the magnetic order parameters have weak but significant coupling with strain. Even at strain magnitudes of ∼0.1–1‰, polaron-like strain effects are clearly important in defining the development and evolution of magnetoelectric properties in these materials. Strains associated with the cubic–orthorhombic transition due to the combined Jahn–Teller/octahedral tilting transition in the vicinity of 1500 K are 2–3 orders of magnitude greater. It is inevitable that ferroelastic twin walls due to this transition would have significantly different magnetoelectric properties from homogeneous domains due to magnetoelastic coupling with steep strain gradients

Magnetic and Transport Properties of PrNi Single Crystal

Frequency dependence of χ"(T), different position of a maximum in χ"(T) for different crystal orientations, hysteretic behavior between magnetization measurements in zero-field cooling and field coolding regime are attributed to strong magneto-crystalline anisotropy of PrNi ferromagnetic single crystal with $T_C$=20.5 K, which is driven by crystal field effect. Applied pressure shifts $T_C$ to higher temperatures ($dT_C$/dp=1 K/GPa). Susceptibility follows the Curie-Weiss law except for b-axis, which is hard magnetic axis. An anisotropic behavior was seen in resistivity measurements with the largest difference between b-axis and c-axis. Resistivity below $T_C$ can be described by power law with $ρT^{2.24}$ and is field dependent with a positive magnetoresistance

Magnetic Properties of Thorium Ferricyanide

The magnetic properties of Th$\text{}_{3}$[Fe(CN)$\text{}_{6}$]·10H$\text{}_{2}$O were investigated. It was shown that this compound is antiferromagnetically ordered in the low temperature region. The observed antiferromagnetic ordering is stable only in the low field

Magnetic Properties of La0.8K0.2MnO3La_{0.8}K_{0.2}MnO_{3} Nanoparticles

Magnetic properties of $La_{0.8}K_{0.2}MnO_{3}$ have been studied on nanoparticles prepared by glycine-nitrate method. Crystal structure and particles size were modified by heat treatment. Crystal structure changes from orthorhombic (space group Pbma) to rhombohedral (space group R-3c) after annealing at 600°C/2 hours. The average size of particle varies with annealing from about 30 nm to 135 nm. The Curie temperature $T_{C}$ and the saturated magnetization $μ_{s}$ increase with annealing. The exchange bias effect was observed on samples with particles size smaller than 60 nm

The Effect of Pressure on Magnetic Properties of KMnCr(CN)

In the contribution we present the effect of pressure on magnetic properties of molecule based magnet KMnCr(CN)6. Applied pressure affects magnetization curves only marginally. The saturation is reached at higher magnetic fields under pressure, but the effect of the pressure on the values of saturated magnetization µs, remnant magnetization µr and coercive field HC are almost negligible. Observed pronounced increase of the Curie temperature TC with increasing pressure can be attributed to strengthening of antiferromagnetic superexchange interaction. Additionally we observed double magnetic transition induced by hydrostatic pressure. All pressure changes were fully reversible

Effect of doping and annealing on crystal structure and magnetic properties of La₁–xAgxMnO₃ magnetic nanoparticles

We study crystal structure and magnetic properties of La₁–xAgxMnO₃ nanopowders prepared by glycine—nitrate method. The particle size and crystal structure were modified by heat treatment. The average size of particle varies from about 26.6(4) nm for as prepared sample to 63.3(9) nm for annealed sample at 900 °C/2 h. Crystal structure changes from orthorhombic Pnma to rhombohedral R3⎯⎯c after annealing at 600 °C/2 h. The saturated magnetization μs and the Curie temperature TC increase with annealing; TC is more than doubled after annealing at 600 °C/2 h. Exchange bias phenomena were first observed on nanoparticles with orthorhombic crystal structure. The hysteresis loop shifts in horizontal and vertical direction after cooling in magnetic field μ₀Hcf ≠ 0 through TC. The values of exchange bias field μ₀HE, coercive field μ₀Hc, remnant asymmetry μE and coercive magnetization μc increase with increasing value of cooling field μ₀Hcf. In addition the training effect was observed

Effect of Pressure on Magnetic Properties of Hexacyanochromates

We present the study of pressure effect on magnetic properties of $TM^{2+}_3[Cr^{III}(CN)_6]_2 \cdot nH_2O$ ferrimagnets and ferromagnets (TM = Cr and Co) under pressures up to 0.9 GPa. Applied pressure strengthens super-exchange interaction in $Cr^{2+}$-prussian blue analogues with dominant antiferromagnetic interaction $J_{AF}$ leading to increase in the Curie temperature $T_C$ (ΔT_c/Δp = 29.0 K/GPa) and reduces $T_C$ of $Co^{2+}$-prussian blue analogues with dominant ferromagnetic interaction $J_F$ (Δ$T_c$/Δp = -1.8 K/GPa). The rise of $J_{AF}$ interaction is attributed to the enhanced value of the single electron overlapping integral S. On the other hand, the applied pressure slightly affects bonding angles between magnetic ions mediated by the cyano-bridge and reduces the strength of magnetic coupling. Changes of the magnetization curve with pressure can be attributed to changes of magnetic anisotropy. The reduction of magnetization with pressure observed on $Cr^{2+}$-prussian blue analogues can be explained by pressure induced transition from $Cr^{2+}$ high spin state to $Cr^{2+}$ low spin state. All pressure induced changes are reversible

Magnetic Properties of La

Magnetic properties of La0.8K0.2MnO3have been studied on nanoparticles prepared by glycine – nitrate method. As prepared nanoparticles and samples annealed at 300°C/2 hours adopt orthorhombic crystal structure (space group Pbnm). Crystal structure and particles size were modified by heat treatment. The exchange bias effect was observed on samples with particles size smaller than 50 nm.Cooling in magnetic field Hcf≠ 0 through the Curie temperature TCshifts hysteresis loop in horizontal and vertical direction. The values of exchange bias field HE, coercive field Hc, remnant asymmetry μE and coercive magnetization μc increase with increasing value of cooling field Hcf. In addition the training effect was studied. Basic magnetic properties like the Curie temperature TC and the saturated magnetization μsincrease and HE or μE decrease with heat treatment. Heat treatment at 600 °C/2 hours increases the average size of nanoparticles to about 60 nm, crystal structure changes to rhombohedral structure (space group R$\bar 3$c) and EB effect vanishes