Showing papers on "Antiferromagnetism published in 1972"
TL;DR: In this paper, the temperature dependences of the thermoelectric power and the low-field magnetic susceptibility for Fe alloys were made of the temperature dependent on the temperature.
Abstract: In an attempt to characterize the magnetic ordering in $\mathrm{Au}\mathrm{Fe}$ alloys, systematic studies were made of the temperature dependences of the thermoelectric power $S$ and the low-field magnetic susceptibility $\ensuremath{\chi}$ for Fe concentrations $C$ from 1 to 22 at.%. The concentration dependences of the magnitude and temperature of the maximum in $S(T)$ showed transitions clearly related to the magnetic ordering. Data analyses based on molecular field theories indicate the existence of small regions of short-range ferromagnetic order which undergo longrange interactions as the temperature is lowered. For $C\ensuremath{\gtrsim}12$ at.%, long-range ferromagnetism is dominant. Lower-concentration alloys ($C\ensuremath{\lesssim}12$ at.%) exhibit an antiferromagnetism with some properties similar to those of a magnetic spin-glass, but with well-defined ordering temperatures characterized by sharp cusps in $\ensuremath{\chi}(T)$, and with a negative Curie $\ensuremath{\theta}$ for $C=1 \mathrm{and} 2$ at.%. These properties indicate a more perfect antiferromagnetic order than that expected for a random alloy or a spin-glass, and this may be related to preferred local lattice arrangements in these alloys.
600 citations
TL;DR: In this article, a theoretical model is developed for coupled-film systems consisting of an underlying ferromagnetic thin film and a surface layer of antiferromagnetic material viewed as an assembly of uniaxial small particles.
Abstract: A theoretical model is developed for, and applied to, some coupled‐film systems consisting of an underlying ferromagnetic thin film and a surface layer of antiferromagnetic material viewed as an assembly of uniaxial small particles. The magnetization of the film biases, and is in turn biased by, the particles through an interfacial exchange coupling. Above a blocking temperature, dependent on size, particles are able to reverse rapidly due to thermal fluctuation, thus exhibiting superparamagnetic response. By assuming a physically reasonable distribution of particle sizes, good agreement is obtained between computed curves for temperature and frequency dependence of hysteresis loop displacement and coercivity based on this model and corresponding experimental results for oxidized Permalloy films, reported in a companion paper. This thermal fluctuation model is also applied successfully to the case of oxidized cobalt films as studied by Schlenker. In this case it is necessary to include in the analysis the...
289 citations
TL;DR: In this article, the magnetic susceptibility at absolute zero temperature for the one-dimensional Hubbard model is studied exactly as a function of the concentration of electrons by using Lieb and Wu's theory for this system.
Abstract: The magnetic susceptibility at absolute-zero temperature for the one-dimensional Hubbard model is studied exactly as a function of the concentration of electrons by using Lieb and Wu's theory for this system. Our analysis essentially follows Griffiths's method for the magnetic susceptibility of the one-dimensional Heisenberg antiferromagnet, and is a generalization of Takahashi's calculation to the systems with an arbitrary concentration of electrons. The ground-state energy and the magnitude of local moments at each site are also studied. Combined with the results on the susceptibility, they should suggest how the effect of the Coulomb interaction on the properties of the system at low temperatures changes with the concentration of electrons.
199 citations
TL;DR: In this article, it was shown that in these compounds the π-type interactions dominate and the ferrimagnetism is rationalized by showing that π type interactions dominate.
176 citations
TL;DR: In this paper, the authors studied the metal-insulator transition due to correlations between electrons using a Hubbard model and showed that the material remains insulating through the Neel temperature.
Abstract: We study the metal-insulator transition due to correlations between electrons using a Hubbard model. Neglecting fluctuations in charge, we only take into account fluctuations in spin density which build up magnetic moments on each site. A close analogy with binary alloys follows from this. At zero temperature, with increasing value of the ratio of the interaction between electrons U to the bandwidth W, we obtain successively a non magnetic metal, an antiferromagnetic one and an antiferromagnetic insulator. This is due, as in Slater's idea, to the exchange part of the self consistent potential which cannot have the full periodicity of the lattice. As it is possible to find a solution with lower energy and with antiferromagnetism to Hubbard hamiltonian, one can construct a self consistent solution with random but non zero moments on each site. The alloy analog of the metal insulator transition is band splitting. For large values of the ratio U/W, the material remains insulating through the Neel temperature. For intermediate values, the line boundary between a Pauli metal and a paramagnetic insulator shows that the insulating phase is favoured at high temperature because of the entropy disorder. We draw a general schematic phase diagram for the Hubbard model and we discuss the relevance of the theory to transition metal oxides. The main qualitative features are consistent with our theory.
156 citations
TL;DR: In this paper, the magnetic properties of these phases are discussed in relation to crystal field effects and a possible band structure.Magnetic measurements from 1.5 to 300 K on the complete series of Cu3Au-type R Pd3 phases have been made.
Abstract: Magnetic measurements from 1.5 to 300 K on the complete series of Cu3Au-type R Pd3 phases have been made. LaPd3 and LuPd3 are diamagnetic at room temperature. CePd3 shows Pauli-type paramagnetism indicative of a nonmagnetic virtual bound state. PrPd3 and NdPd3 are affected at low temperatures by the presence of the crystal field. The magnetic properties of SmPd3 and EuPd3 are determined by the energy levels of the lowest multiplet. GdPd3 and (possibly) TbPd3 become antiferromagnetic at 7.5 and 2.5 K respectively. DyPd3-ErPd3 obey the Curie law. The magnetic properties of these phases are discussed in relation to crystal field effects and a possible band structure.
122 citations
TL;DR: SrCoO 2.5 with brownmillerite (4CaO·Fe 2 O 3 ·Al 2O 3 ) type structure is an antiferromagnet with the Neel temperature of 570 K.
Abstract: SrCoO 2.5 with brownmillerite (4CaO·Fe 2 O 3 ·Al 2 O 3 ) type structure is an antiferromagnet with the Neel temperature of 570 K. The magnetic structure as determined from a neutron diffraction study is of G-type and the Co 3+ magnetic moment is 3.3±0.5µ B at liquid nitrogen temperature.
111 citations
TL;DR: In this article, the magnetic phase diagram of the antiferromagnetic structure of a typical layer-type ferromagnet has been established and the differential magnetic susceptibility χ = (∂M/∂H)T of (C2H5NH3)2CuCl4 has been studied as a function of an extra external field (0-2 kOe) and of temperature (1-30 K; Tc = 10.20 K).
110 citations
TL;DR: Extended series expansions for the high temperature zero-field susceptibility of the Ising model are given in powers of the usual high temperature counting variable v=tanh K; for the triangular lattice to v16, for the square lattice and for the honeycomb lattice, inclusive.
Abstract: Extended series expansions for the high temperature zero-field susceptibility of the Ising model are given in powers of the usual high temperature counting variable v=tanh K; for the triangular lattice to v16, for the square lattice to v21 and for the honeycomb lattice to v32, inclusive. The asymptotic behaviour of the ferromagnetic and antiferromagnetic susceptibility is studied. It is concluded that the ferromagnetic singularity is not exactly factorizible. The antiferromagnetic susceptibility of the square and honeycomb lattices has a singularity of the same type as the energy at the antiferromagnetic critical temperature.
105 citations
TL;DR: Samples of the system SrCo 1- x Fe x O 3- y (0≤ x ≤ 1, 0≤ y ≤ 0.5) have been prepared under varying oxygen pressure and temperature and their crystal-lographic and magnetic properties have been studied.
Abstract: Samples of the system SrCo 1- x Fe x O 3- y (0≤ x ≤1, 0≤ y ≤0.5) have been prepared under varying oxygen pressure and temperature and their crystal-lographic and magnetic properties have been studied. SrCoO 2.5 with brown-millerite type structure (high temperature phase) is an antiferromagnet with the Neel temperature of 570 K and the Co 3+ -O 2- -Co 3+ superexchange interaction is strongly antiferromagnetic. SrCoO 3 and SrCo 1- x Fe x O 3 ( x <0.9) with the cubic perovskite structure (high temperature phase) are ferromagnetic with the Curie temperature at about 200 K and the magnetization decreases rapidly with increasing x near SrFeO 3 whose magnetic structure is helical.
105 citations
TL;DR: In this article, the magnetic susceptibility of a series of tetragonal compounds of general formula (C n H 2 n +1 NH 3 ) 2 MnCl 4 (n = 1,2,3,…) was measured.
TL;DR: Magnetic and Mossbauer effect measurements on the nitrides with hcp metal lattice of V, Cr, Mn and Fe are carried out as a function of composition as mentioned in this paper.
Abstract: Magnetic and Mossbauer effect measurements on the nitrides with hcp metal lattice of V, Cr, Mn and Fe are carried out as a function of composition. Hexagonal VN x and hexagonal CrM x are Pauli paramagnetic. Hexagonal MnN x shows antiferromagnetism, while both hexagonal and orthorhombic FeN x show ferromagnetism at low temperatures. In these Phases, nitrogen atoms suppress magnetic ordering in consequence of the reduction of magnetic moments. As a whole, the observed types of magnetism of hexagonal nitrides resemble those of their metals in spite of the difference in crystal structures. Type II superconductivity is found in hexagonal VN x although it is not yet conclusive.
TL;DR: In this article, the authors investigated the thermodynamic properties of a linear chain of elastically coupled spins with an antiferromagnetic interaction between them in the XY model and the adiabatic approximation.
Abstract: We investigate the thermodynamic properties of a linear chain of elastically coupled spins with an antiferromagnetic interaction between them in the XY model and the adiabatic approximation. This system exhibits a second order phase transition and a magnetic susceptibility which vanishes at absolute zero. The effects of magnetostriction are considered and shown to affect neither the order of the transition nor the qualitative behavior of the magnetic susceptibility.
TL;DR: The compound LaRuO3 as mentioned in this paper appears to be metallic and antiferromagnetic and has the orthorhombic GdFeO3-type perovskite structure.
TL;DR: In this article, the authors investigated the metal-non-metal transition due to correlations between electrons in narrow energy bands using a functional integral formalism and found that the splitting of the band is due to antiferromagnetism.
Abstract: We investigate the metal-non-metal transition due to correlations between electrons in narrow energy bands. Using a functional integral formalism, we study Hubbard's model. The insulating properties are found to be consequences of magnetism. At low temperature the splitting of the band is due to antiferromagnetism. Above the Nel temperature, it is due to the formation of local moments on each site.
TL;DR: The magnetic properties and lattice constants of the rare earth tetraborides RB4 have been determined in this paper and it is shown that the ferromagnetic behavior of PrB4 is probably the result of a strong participating of the orbital angular momentum to the indirect exchange coupling between the localized moments.
Abstract: The magnetic properties and the lattice constants of the rare earth tetraborides RB4 have been determined. The compound PrB4 is ferromagnetic. The compounds in which R represents Nd, Sm, Gd, Tb, Dy, and Ho are antiferromagnetic while ErB4 and YbB4 show metamagnetic behavior. The element Ce and to some extent also the element Yb show an abnormal valency in the tetraborides. The magnetic properties of the RB4 compounds are discussed in terms of the RKKY formalism. It is shown that the ferromagnetic behavior of PrB4 is probably the result of a strong participating of the orbital angular momentum to the indirect exchange coupling between the localized moments.
TL;DR: In this paper, single crystals of Cr 3 Te 4 with the pseudo-NiAs type structure have been made by chemical transport method in order to investigate the anomaly below 80 K. But on contrary to his result, the easy axis of the moment is parallel to the c-axis in the whole ferromagnetic region and antiferromagnetic order appears only in the c -plane.
Abstract: Single crystals of Cr 3 Te 4 with the pseudo-NiAs type structure have been made by chemical transport method in order to investigate the anomaly below 80 K. The saturation moment at 4.2 K is equal to 1.79±0.03 µ B per Cr 1- x Te (x=0.25), and the Curie temperature is 316 K. The magnetization only in the direction to the a -axis shows the anomaly that the saturation field increases abruptly below 80 K, which corresponds to the Neel point proposed by Andresen. But on the contrary to his result, the easy axis of the moment is parallel to the c -axis in the whole ferromagnetic region and antiferromagnetic order appears only in the c -plane. By a spin echo method, two nuclear magnetic resonance absorption lines of Cr 53 -nuclei are observed at 45.3 and 57.5 MHz at 4.2 K. The resonance frequencies increase remarkably below 80 K. This fact may support subsidiarily the existence of the antiferromagnetic order below 80 K.
TL;DR: In this paper, the ground state spin arrangements in magnetic compounds of the NaCl type structure are studied by consideration of exchange interactions between nearest neighbors (J 1 ) and between next-nearest neighbours (J 2 ).
Abstract: The ground state spin arrangements in magnetic compounds of the NaCl type structure are studied by consideration of exchange interactions between nearest neighbors ( J 1 ) and between next-nearest neighbors ( J 2 ). Ferromagnetic arrangement as well as antiferromagnetic arrangements of the first kind, second kind, and improved first kind are obtained in different intervals of the parameter γ= J 2 / J 1 . Each of the three antiferromagnetic arrangements is degenerate due to the cubic symmetry of the crystal and the spin arrangement indefinite. Since the monoxides of the iron group elements are slightly distorted below the Neel point, the relevant small changes in J 1 and J 2 are taken into account to see if the degeneracy is removed. It turns out that the degeneracy is removed partially or completely. Helical spin arrangements appear in certain intervals of γ. Finally, anisotropy energy of the form D S z 2 is taken into account, but the degeneracy still remains unlifted in some cases.
TL;DR: In this article, the angular dependence of line width at room temperature can be quantitatively explained by taking account of the spin diffusion effect in addition to the dipolar and anisotropic exchange interactions under a strong one-dimensional antiferromagnetic exchange interaction.
Abstract: Precise temperature and angular dependences of ESR line in a typical linear chain antiferromagnet Cu(C 6 H 5 COO) 2 3H 2 O were measured in a temperature region from 1.4 to 300 K over a microwave frequency range from 10 to 48 GHz. The angular dependence of line width at room temperature can be quantitatively explained by taking account of the spin diffusion effect in addition to the dipolar and anisotropic exchange interactions under a strong one-dimensional antiferromagnetic exchange interaction. At low temperatures, the line width along the a ''-axis becomes narrow at temperature decreases whereas it becomes unmeasurably broad and shows a strong frequency dependence along the c ''-axis. The g -shift due to the one-dimensional antiferromagnetic spin correlations was also found at low temperatures.
TL;DR: In this paper, the first order antiferromagnetic-ferromagnetic transition of the equiatomic FeRh alloy is investigated thermodynamically and the phonon, conduction electron and magnon contributions to the free energy of both phases are calculated numerically.
Abstract: The first order antiferromagnetic-ferromagnetic transition of the equiatomic FeRh alloy is investigated thermodynamically. The phonon, conduction electron and magnon contributions to the free energy of both phases are calculated numerically. The results predict a parabolic temperature dependence of the critical field required to induce the transition which is in agreement with experiment. The calculated value of the entropy change at the transition is 14Jkg-1K-1 which agrees with the measured values. The pressure dependence of the critical field is discussed and shown to be consistent with the model. Evidence is given that an ordered magnetic moment exists on the rhodium atoms in the antiferromagnetic state.
TL;DR: The static magnetic susceptibility from 1.6 to 300°K and the heat capacity in fields of 0 and 5 kG from 0.9 to 10.2°K have been measured on polycrystalline samples of the complex of 1,3-bisdiphenylene-2-phenylallyl with benzene, commonly abbreviated BDPA.
Abstract: The static magnetic susceptibility from 1.6 to 300°K and the heat capacity in fields of 0 and 5 kG from 0.9 to 10.2°K have been measured on polycrystalline samples of the complex of 1,3‐bisdiphenylene‐2‐phenylallyl with benzene, commonly abbreviated BDPA. The data are shown to correspond to antiferro‐magnetic Heisenberg linear chains characterized by a nearest‐neighbor exchange integral of −4.6°K. Weak interchain coupling results in a paramagnetic—antiferromagnetic phase transition at 1.695°K in zero field, as evidenced by the sharp heat capacity anomaly at that temperature. Resolution of the heat capacity into a lattice T3 contribution and a magnetic contribution yields a Debye temperature of 52.5°K and a magnetic entropy per mole of 101% of the expected Rln2.
TL;DR: The spin structure of the metallic hexagonal B 35 phase of FeGe has been studied by means of susceptibility and magnetization measurements as discussed by the authors, and it has been shown that the spins then form a double cone structure with a cone halfangle of 20° at 4.2 K. The result is in good agreement with Fermi surface calculations by Sundstrom (Physica Scripta, following paper, which show the existence of several spin density wave vectors between Q = 0.89 π/c and Q = 1.3 π /c calipering different parts
Abstract: The spin structure of the metallic hexagonal B 35 phase of FeGe has been studied by means of susceptibility and magnetization measurements. Below the Neel temperature TN = 411 K hexagonal FeGe is a uniaxial antiferromagnet with the spins parallel to the c-axis. In each c-plane all spins are ferromagnetically coupled with an exchange constant J0 ≈ 22 meV. The antiferromagnetic exchange constant between nearest neighbour and next nearest neighbour c-planes are J1 = -3.5 meV and J2 = -0.9 meV resp. in the molecular field model. Susceptibility and spin flop experiments indicate that the spins tilt away from the c-axis below 30 K. We suggest that the spins then form a double cone structure with a cone halfangle of 20° at 4.2 K. In the double cone the c-plane components have a turn angle in the vicinity of 180° between nearest neighbour planes, which implies absence of long range order. The result is in good agreement with Fermi surface calculations by Sundstrom (Physica Scripta, following paper), which show the existence of several spin density wave vectors between Q = 0.89 π/c and Q = 1.3 π/c calipering different parts of the Fermi surface in a direction parallel to the c-axis.
TL;DR: The first transition series diborides are isomorphous compounds from ScB 2 to MnB 2 and they all show metallic behaviour and are paramagnetic up to VB 2 ; CrB 2, on the contrary, is antiferromagnetic with a small magnetic moment value in the ordered state which suggests the occurrence of itinerant spin magnetism as mentioned in this paper.
TL;DR: In this article, the magnetic properties of Mn(OH)2 were investigated between 4.2 and 273 K. The magnetic superlattice reflections were indexed on the basis of a hexagonal unit cell with the dimensions a M = a (3), and cM = 2c where a = 3.322 A and c = 4.734 A are the dimensions of the chemical unit cell.
TL;DR: In this article, the magnetic properties and microstructures of the vanadium phosphate glass system over the composition range 60 to 90 mol% V2O5 were investigated to study magnetic ordering in the glass and the effect of microstructure on its magnetic properties.
Abstract: The magnetic properties and microstructures of the vanadium phosphate glass system over the composition range 60 to 90 mol% V2O5 were investigated to study magnetic ordering in the glass and the effect of microstructure on its magnetic properties. Direct antiferromagnetic coupling between V4+ ions in the glassy matrix exists, and a transition temperature near - 70°C was observed. As-cast glasses with high V2O5 concentrations separated into two glassy phases; this separation increased the ESR line width as a result of inhomogeneity broadening. The separation, which concentrated the vanadium ions in a vanadium-rich phase, caused a hysteresis in the plot of ESR line intensity vs temperature at the transition temperature. Reduction of the vanadium ions by dextrose added to the melt enhanced phase separation and resulted in weak antiferromagnetic transitions at +70° and -120°C, the Neel temperatures of VO2 and V2O3, respectively.
TL;DR: In this article, three modifications of barium manganese oxide, BaMnO3(2H), BMo3(9R), and BMo 3(4H) were prepared using hydrothermal and high-pressure techniques.
TL;DR: In this paper, the de Haas van Alphen effect was studied in very dilute copper-based alloys of Cr, Mn, Fe, and Co. The results indicated an antiferromagnetic interaction between conduction electrons and polarized impurity spins with very little Kondo screening.
Abstract: Modification of the Zeeman splitting of conduction-electron spins by an s–d exchange interaction has been studied in the de Haas – van Alphen effect at fields up to 50 kG and temperatures of order 1 K in very dilute copper-based alloys of Cr, Mn, Fe, and Co. In Cu(Cr) there is a linear relationship between an effective exchange energy and solute concentration, and the results indicate an antiferromagnetic interaction between conduction electrons and polarized impurity spins with very little Kondo screening. The effects of increasing field or decreasing temperature are consistent with a simple polarization of the impurity spins. The variation of the exchange energy from orbit to orbit is explained by the variation over the copper Fermi surface of the d-like part of the wave function. The occurrence of clean spin-splitting zeros in the Cu(Cr) system is believed to be a fortuitous result of a symmetrical positioning of the Friedel virtual bound states relative to the Fermi energy. In Cu(Mn) the exchange ener...
TL;DR: In this article, the depression of the superconducting transition temperature by a system of correlated moving spins is calculated using a variational procedure, and corrections to the Abrikosov-Gorkov theory in the neighbourhood of a magnetic phase transition are examined.
Abstract: Using a variational procedure, the depression of the superconducting transition temperature by a system of correlated moving spins is calculated. In particular, corrections to the Abrikosov-Gorkov theory in the neighbourhood of a magnetic phase transition are examined. Characteristic differences in the concentration dependence of the superconducting transition temperature are found in the cases of ferromagnetic and antiferromagnetic spin correlations.