Search results for "Curie–Weiss law"
showing 10 items of 11 documents
Ferromagnetic and paramagnetic magnetization of implanted GaN:Ho,Tb,Sm,Tm films
2015
The SQUID magnetic measurements were performed on the GaN films prepared by metal-organic vapour phase epitaxy and implanted by Tb3+, Tm3+, Sm3+, and Ho3+ ions. The sapphire substrate was checked by the electron paramagnetic resonance method which showed a content of Cr3+ and Fe3+ impurities. The samples 5 × 5 mm2 were positioned in the classical straws and within an estimated accuracy of 10−6 emu, no ferromagnetic moment was detected in the temperature region of 2–300 K. The paramagnetic magnetization was studied for parallel and perpendicular orientation. In the case of GaN:Tb sample, at T = 2 K, a pronounced anisotropy with the easy axis perpendicular to the film was observed which can b…
Itinerant Electron Metamagnetism in η-Carbide-Type Compound Co3Mo3C
2010
We report the magnetic properties of the cobalt molybdenum η-carbide-type compounds Co 3 Mo 3 C and Co 3 Mo 3 N. The magnetic susceptibility χ of Co 3 Mo 3 C shows a Curie–Weiss temperature dependence at high temperatures and a broad maximum at around 100 K, whereas that of Co 3 Mo 3 N shows a nearly temperature-independent enhanced Pauli paramagnetic behavior. The absence of a magnetic long-range order was confirmed by the nuclear magnetic resonance technique in both the compounds. As expected from the broad maximum of χ, we observed an itinerant electron metamagnetic transition at around 37 T in Co 3 Mo 3 C.
Ferromagnetic ordering in GdPdCd
2010
Abstract GdPdCd was obtained in pure form via reaction of the elements in a sealed tantalum tube in a high-frequency furnace. The structure was investigated by X-ray diffraction on both powders and single crystals: ZrNiAl type, P 6 2m , a=758.2(1), c=391.78(7) pm, wR2=0.0410 for 358 F2 values and 14 variables. Striking structural motifs of GdPdCd are two types of palladium-centered tricapped trigonal prisms [Pd1Cd3Gd6] and [Pd2Cd6Gd3]. Together the palladium and cadmium atoms build a three-dimensional network in which the gadolinium atoms fill distorted pentagonal channels. Susceptibility measurements reveal Curie–Weiss behaviour with an effective magnetic moment of 8.2(1) μB/Gd. GdPdCd ord…
Structural, electronic, and magnetic properties of tetragonalMn3−xGa: Experiments and first-principles calculations
2008
This work reports on the electronic, magnetic, and structural properties of the binary intermetallic compounds ${\mathrm{Mn}}_{3\ensuremath{-}x}\mathrm{Ga}$. The tetragonal ${\mathrm{DO}}_{22}$ phase of the ${\mathrm{Mn}}_{3\ensuremath{-}x}\mathrm{Ga}$ series, with $x$ varying from 0 to 1.0 in steps of $x=0.1$, was successfully synthesized and investigated. It was found that all these materials are hard magnetic, with energy products ranging from $10.1\phantom{\rule{0.3em}{0ex}}\mathrm{kJ}\phantom{\rule{0.2em}{0ex}}{\mathrm{m}}^{\ensuremath{-}3}$ for low Mn content $(x\ensuremath{\rightarrow}1)$ to $61.6\phantom{\rule{0.3em}{0ex}}\mathrm{kJ}\phantom{\rule{0.2em}{0ex}}{\mathrm{m}}^{\ensurema…
Magnetization and61Ni Mössbauer effect study of the ternary arsenide CrNiAs
2008
The results of x-ray diffraction, dc magnetization, and 61Ni M?ssbauer spectroscopy studies of the ternary arsenide CrNiAs are reported. This compound crystallizes in the orthorhombic Fe2P-type structure (space group ) with the lattice parameters a = 6.1128(2)?? and c = 3.6585(1)??. CrNiAs is a mean-field ferromagnet with Curie temperature TC = 171.9(1)?K and the critical exponents ? = 0.514(18), ? = 1.010(16), and ? = 2.922(10). The temperature dependence of the magnetic susceptibility above TC follows the modified Curie?Weiss law with a paramagnetic Curie temperature of 176.0(3)?K and effective magnetic moment per transition metal atom of 2.42(1)??B. The magnetic moment per formula unit a…
Grain-size-induced relaxor properties in nanocrystalline perovskite films
2004
Thin films of ${\mathrm{Pb}}_{0.76}{\mathrm{Ca}}_{0.24}{\mathrm{TiO}}_{3}$ (PTC), which is a classical ferroelectric as a bulk material and of the relaxor material $\mathrm{Pb}({\mathrm{Sc}}_{0.5}{\mathrm{Nb}}_{0.5}){\mathrm{O}}_{3}$, have been produced to find out whether nanocrystalline ferroelectric films show a grain-size-induced relaxor behavior. Amorphous films were deposited onto a $\mathrm{Ti}∕\mathrm{Pt}$ coated silicon (100) wafer by reactive $\text{rf}$ sputtering. Different grain sizes were prepared by a controlled annealing process and they were determined by profile analysis of x-ray diffraction spectra. Temperature dependent Raman spectroscopy was used to look for phase trans…
Geometric, electronic, and magnetic structure ofCo2FeSi: Curie temperature and magnetic moment measurements and calculations
2005
In this work a simple concept was used for a systematic search for materials with high spin polarization. It is based on two semiempirical models. First, the Slater-Pauling rule was used for estimation of the magnetic moment. This model is well supported by electronic structure calculations. The second model was found particularly for ${\mathrm{Co}}_{2}$ based Heusler compounds when comparing their magnetic properties. It turned out that these compounds exhibit seemingly a linear dependence of the Curie temperature as function of the magnetic moment. Stimulated by these models, ${\mathrm{Co}}_{2}\mathrm{FeSi}$ was revisited. The compound was investigated in detail concerning its geometrical…
Structure and magnetic properties of AgFeP2O7
2010
Abstract AgFeP2O7 has been synthesized by flux crystallization and characterized by single crystal and powder X-ray diffraction (sp. gr. P21/c, a=7.3298(2), b=7.9702(2), c=9.5653(2) A, β=111.842(1)°, V=518.68(2) A3) and FTIR-spectroscopy. The structure is composed of isolated iron octahedra and phosphate tetrahedra interconnected into 3D network with hexagonal channels, where silver counter-ions are located. The magnetic behavior of the compound approaches the Curie–Weiss equation with a Weiss constant θ=−165.9 K indicating strong antiferromagnetic interaction between iron(III) ions.
Manifestation of Curie-Weiss law for optical phase transition
2001
Considerable slowing down is observed for both the temporal development of the coherent oscillation slightly above the threshold and the refractive index grating decay slightly below the threshold for a semilinear photorefractive oscillator with two counter-propagating pump waves. It is shown that in the vicinity of the threshold the reciprocal characteristic time is a linear function of deviation from the threshold coupling strength. This behaviour is similar to an empirical Curie–Weiss law and points to the analogy of the oscillation threshold to a second-order phase transition.
Magnetic and electronic properties of double perovskites and estimation of their Curie temperatures byab initiocalculations
2008
First principles electronic structure calculations have been carried out on ordered double perovskites Sr_2B'B"O_6 (for B' = Cr or Fe and B" 4d and 5d transition metal elements) with increasing number of valence electrons at the B-sites, and on Ba_2MnReO_6 as well as Ba_2FeMoO_6. The Curie temperatures are estimated ab initio from the electronic structures obtained with the local spin-density functional approximation, full-potential generalized gradient approximation and/or the LDA+U method (U - Hubbard parameter). Frozen spin-spirals are used to model the excited states needed to evaluate the spherical approximation for the Curie temperatures. In cases, where the induced moments on the oxy…