Showing papers on "Antiferromagnetism published in 1982"
TL;DR: In this article, it was shown that the only one-particle excitation in the Heisenberg antiferromagnetic chain of arbitrary spins is a doublet of spin 12 spin waves.
440 citations
TL;DR: In this article, it was shown rigorously that the one-dimensional Ising model with long-range antiferromagnetic interactions exhibits a complete devil's staircase, which is the same as the one in this paper.
Abstract: It is shown rigorously that the one-dimensional Ising model with long-range antiferromagnetic interactions exhibits a complete devil's staircase.
330 citations
TL;DR: In this paper, a numerical method was developed to study the scaling of distribution of couplings of highly random antiferromagnetic Ising and quantum Heisenberg spin-\textonehalf{} systems.
Abstract: A numerical method is developed to study the scaling of distribution of couplings of highly random antiferromagnetic Ising and quantum Heisenberg spin-\textonehalf{} systems. The method shows how freezing into inert local singlets prevents ordering down to temperatures well below the median nearest-neighbor coupling or bare exchange percolation threshold in positionally disordered systems with Heisenberg exchange varying exponentially with distance (e.g., doped semiconductors, quasi one-dimensional salts). This is contrasted with the Ising system.
275 citations
TL;DR: The mpx3 phases (M = Mn, Fe, Ni; X = S, Se) with sheet structures are insulators with localized moments and show antiferromagnetic ordering at low temperatures as discussed by the authors.
182 citations
TL;DR: In this paper, the ground state properties of the one-dimensional spin-s (12⩽s <∞) anisotropic XYZ antiferromagnet in a magnetic field of arbitrary direction were studied.
Abstract: This is a study of the ground-state properties of the one-dimensional spin-s (12⩽s<∞) anisotropic XYZ antiferromagnet in a magnetic field of arbitrary direction. It provides the first rigorous results for the general case of this model in non-zero field. By exact calculations we find the existence of an ellipsoidal surface h = hN in field space where the ground state is of the classical two-sublattice Neel type with non-zero antiferromagnetic long-range order. At hN there are no correlated quantum fluctuations. We give upper and lower bounds for the critical field hc where antiferromagnetic long-range order is suppressed by the field. The zero-temperature phase diagrams are discussed for a few representative cases.
180 citations
08 Sep 1982
TL;DR: In this article, the critical temperature of the antiferromagnetic q-state Potts model on the square lattice is located, and the critical free energy and internal energy are evaluated.
Abstract: The critical temperature of the antiferromagnetic q -state Potts model on the square lattice is located, and the critical free energy and internal energy are evaluated. As with the ferromagnetic model, the transition is continuous for q ≼4, and its first-order (i. e. has latent heat) for q >4. However, only for q ≼3 can the critical temperature be real. For the isotropic model the criticality condition is exp( J / k T ) = -1 + (4- q ) ½ .
152 citations
TL;DR: In this paper, the coercive force of Fe92Zr8 amorphous alloy drastically increases below 30 K, and the high-field susceptibility of the present alloys are extremely large.
Abstract: Several kinds of Fe‐Zr amorphous ribbons have been prepared from the melt in an argon atmosphere, and the spin‐glass‐like behaviors have been investigated. The thermomagnetic history has been observed, and the freezing temperature monotonously decreases, in contrast to the Curie temperature, which increases and then goes through a maximum with increasing Zr content. Asymmetric hysteresis loops and the relaxation of remanence have also been found. The coercive force of Fe92Zr8 amorphous alloy drastically increases below 30 K, and the high‐field susceptibility of the present alloys are extremely large. These behaviors are explained in terms of the coexistence of ferromagnetic and antiferromagnetic states.
126 citations
TL;DR: A Mossbauer spectroscopic study on a series of aluminum-substituted hematites, α(Fe1-cAlc)2O3, with c up to 0.32 is reported in this paper.
106 citations
TL;DR: In this article, a systematic treatment of the equation of motion of the classical anisotropic Heisenberg spin chain is given, both in the discrete case and in the continuum limit, in which the spins associated with the lattice sites m are replaced by a spin density S(x, t), which is a function of the time t and the position x on the chain.
Abstract: A systematic treatment is given of the equation of motion of the classical anisotropic Heisenberg spin chain, both in the discrete case and in the continuum limit in which the spins Sm(t) associated with the lattice sites m are replaced by a spin density S(x, t), which is a function of the time t and the position x on the chain. In the case of axial symmetry the equation of motion for the spins is shown to be equivalent to a new equation in terms of one real variable, i.e. qm(t) in the discrete case q(x, t) in the continuum limit. (From the treatment by A.E. Borovik it follows that the new equation of motion for q(x, t) is completely integrible in the special case of quadratic anisotropy.) Explicit expressions are given for the Lagrangians, both in the ferromagnetic and in the antiferromagnetic case. The relation with the nonlinear Schrodinger equation on the one hand and the sine-Gordon equation on the other hand is discussed in some detail.
101 citations
TL;DR: In this paper, a review of surface magnetic order (SMO) of ferromagnetic metals can be found, with particular emphasis given to electron-capture spectroscopy.
100 citations
TL;DR: The crystal and magnetic structures of the Co x Ni 1 − x MnGe compounds have been studied by neutron diffraction experiments Magnetic phase diagram has been constructed as mentioned in this paper, the compounds with the low Co concentration have helicoidal magnetic structure The compounds with large Co concentration are ferromagnets
TL;DR: In this paper, the local spin density theory of electronic exchange and correlation is implemented using parameter-free self-consistent energy-band calculations, and the results are used to design new magnetic compounds composed of nonmagnetic elements.
Abstract: The following questions are considered: How do itinerant d electrons of the Heusler alloys produce magnetic moments that are completely localized on the Mn atoms? What is the microscopic origin of Invar anomalies? Why is elemental antiferromagnetism confined to Cr, Mn, and Fe? Why do the Fe atoms in Fe3Si carry two distinctly different magnetic moments? Can we use our understanding of transiton‐metal magnetism to ’’design’’ new magnetic compounds composed of nonmagnetic elements? Our answers to these questions are based on the local‐spin‐density theory of electronic exchange and correlation, implemented using parameter‐free self‐consistent energy‐band calculations.
TL;DR: In this paper, a modified magnetic phase diagram is suggested for the spinel system (AB2O4) in which the A and B sites are partially (or completely) occupied by magnetic atoms.
Abstract: The article by Villain [Z. Phys. B — Condensed Matter33, 31 (1979)] is discussed and a modified magnetic phase diagram is suggested for the spinel system (AB2O4) in which theA andB sites are partially (or completely) occupied by magnetic atoms. This diagram takes into account the antiferromagnetic exchange interactionsJAA,JBB andJAB between nearest neighbor cations of various types. Regions of paramagnetic, antiferromagnetic, ferrimagnetic and possible spin glass behaviour are indicated on the diagram.
TL;DR: In this article, the structure of a lamellar compound with S|Cu 0.33 Cr 0.50 PS 3 is modeled as a two-dimensional Heisenberg model, where copper is not located at the center of its octahedral sites but is distributed among a continuous series of positions within these sites.
TL;DR: In this article, a simple recurrence relation for successive shell magnetizations far removed from the surface has been established for the Ising model on a Cayley tree with zero long-range order at all finite temperatures.
Abstract: The Ising model on a Cayley tree displays a peculiar (continuous order) phase transition with zero long-range order at all finite temperatures. When one studies expection values of spins far removed from the surface (which contains a finite fraction of the total number of spins in the thermodynamic limit), however, one obtains the so-called Bethe approximation. Here we study such a local description by setting up a simple recurrence relation for successive shell magnetizations far removed from the surface. In the ferromagnetic case the local magnetization is a fixed point of the iterative transformation, while in the antiferromagnetic case the fixed point bifurcates to a two-cycle of the transformation (for low temperatures and fields) giving rise to local sublattice magnetizations. In both cases, local thermodynamical properties are obtained by integration.
TL;DR: In this paper, the results for the ferromagnetic system were compared with theoretical predictions derived from a bond-diluted Ising model using the replica method and a second-order variational approximation.
Abstract: Spin glass behaviour has been observed in a very large concentration range in both CdCr2xIn2-2xS4 and ZnCr2xAl2-24 spinel systems. It is a result of the presence in these systems of competing interactions, ferromagnetic between first-nearest neighbours and antiferromagnetic between higher-order neighbours. The ratios between the interactions are such that the non-dilute x=1 compounds are ferromagnetic for the first system and helimagnetic for the second. The entire phase diagrams of both solutions have been determined by very low field AC and DC susceptibility measurements. The results for the ferromagnetic system are compared with theoretical predictions derived from a bond-diluted Ising model using the replica method and a second-order variational approximation.
TL;DR: In this paper, the hyperfine field distributions of Fe91Zr9 were determined from the Mossbauer spectra for 6 K < T < 230 K. As in other alloys with invar behaviour, the distribution consists of a high field peak and a broad low field tail.
TL;DR: In this article, the three-state Potts model on a square lattice with general nearest-neighbor interaction and ferromagnetic second-NEB interaction was studied and an explicit expression for the critical index describing such excitations was obtained.
Abstract: The three-state Potts model on a square lattice with general nearest-neighbor interaction and ferromagnetic second-neighbor interaction is studied. At zero temperature the model with antiferromagnetic nearest-neighbor interactions is mapped to the $F$ model. By comparing the excitations generated at nonzero temperature to those that lead to the eight-vertex model we obtain an explicit expression for the critical index describing such excitations and demonstrate the existence of a critical fan for ferromagnetic second-neighbor interactions. The model with purely nearest-neighbor interactions is critical only at zero temperature. Explicit expressions for the scaling indices of the color-color correlation function in the critical phase are also obtained. Phenomenological renormalization-group methods are applied to determine the general boundaries of the critical fan and to verify our expressions for critical indices. A physical system which might be expected to undergo a transition in the same universality class as that of the above model and to exhibit a critical phase is proposed: an equal mixture of krypton and xenon adsorbed on graphite.
TL;DR: Magnetic properties of the Ce 1- x La x Mn 2 Si 2 system were investigated by means of neutron diffraction and magnetometry in this paper, where it was shown that the type of magnetic ordering depends on the Mn-Mn interatomic distances in the basal plane.
TL;DR: In this article, a detailed analysis of the data based on a magnetic-cluster description of mictomagnetic alloys is presented, and it is shown that these semimagnetic semiconductors do not behave like canonical spinglasses.
Abstract: Magnetic properties of single crystals ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Te}$ ($0.05l~xl~0.5$) have been studied. The low-field susceptibility has been measured for temperatures ranging from 0.07 to 30 K, and is compared with high-field magnetization data. It is shown that these semimagnetic semiconductors do not behave like canonical spin-glasses. A detailed analysis of the data based on a magnetic-cluster description of mictomagnetic alloys is presented. Some features, such as the particular $x$ dependence of the freezing temperature and the coexistence of infinite and finite spin clusters in a definite range of concentrations $x$ above the percolation threshold, are correlated to the short-range nature of the exchange interaction between Mn ions.
TL;DR: In this paper, magnetic susceptibilities and magnetization isotherms have been measured for a single crystal FeTiO 3, where the susceptibility parallcl to the c-axis has a large and sharp peak at T N = 580±03 K, while the perpendicular susceptibility is almost independent of temperature below T N .
Abstract: Magnetic susceptibilities and magnetization isotherms have been measured for single crystal FeTiO 3 The susceptibility parallcl to the c -axis has a large and sharp peak at T N =580±03 K, while the perpendicular susceptibility is almost independent of temperature below T N Magnetization isotherm at 42 K with fields applied along the c -axis exhibits a typical metamagnetic transition at H c =803±01 kOe, being the first observation of metamagnetism in 3 d transition metal oxides The transition is of the first order up to about 35 K, above which it is of the second order The experimental data are well reproduced by molecular field calculations with the best fit parameters of the anisotropy field H A =150 kOe, the ferromagnetic intrasublattice exchange interaction of 2 z 1 J 1 =285 K, and the antiferromagnetic intersublattice interaction of 2 z 2 J 2 =-667 K
TL;DR: In this paper, the authors show that the competition between ferromagnetic nearest neighbor exchange J1 and antiferromagnetic next-nearest neighbor exchange interaction J2 with J2/J1 = −0.5 is shown to cause a breakdown of ferromagnetism in EuxSr1−xS at x = 0.51.
Abstract: Presence of additional antiferromagnet bonds in a ferromagnet changes magnetic ordering in a dilution series drastically. An ideal system to study these effects is the insulating EuxSr1−xS, based on EUS, the well‐known model substance for a Heisenberg ferromagnet. The competition between ferromagnetic nearest neighbor exchange J1 and antiferromagnetic next‐nearest neighbor exchange interaction J2 with J2/J1 = −0.5 is shown to cause a breakdown of ferromagnetism in EuxSr1−xS at x = 0.51, far above the percolation threshold xp = 0.13. In the intermediate concentration regime, 0.13⩽x⩽0.51, spin‐glass behavior is observed very similar to the features in metallic spin glasses. Results on (Eu, Sr)S provide clear evidence for a cooperative phenomenon at the spin‐glass transition, as distinguished from ordinary thermal blocking of superparamagnetic clusters. By increasing the Eu concentration just above xc, long‐range ferromagnetic order is found to coexist with a high amount of wrong aligned spins, which again i...
TL;DR: In this article, the electronic structure of cleaved (100) single crystals of UAsxSe1−x, UxTh 1−xSb, USbxTe1−XSb and UxY1−Sb with high resolution (ΔE <150 meV) photoemission using synchrotron radiation 10⩽hν⩾130 eV was studied.
Abstract: We have studied the electronic structure of cleaved (100) single crystals of UAsxSe1−x, UxTh1−xSb, UxY1−xSb, and USbxTe1−x with high resolution (ΔE<150 meV) photoemission using synchrotron radiation 10⩽hν⩽130 eV. In contrast to the general belief we find significant differences in the photoemission density of states near EF for these compounds. We conclude that these differences are mainly due to valence d electrons and that U has a quasi‐localized 5f3 configuration in resonance with itinerant 6d states. This explains the quite similar magnetic behavior of UxTh1−xSb and USbxTe1−x, both of which change from highly anisotropic 〈100〉 antiferromagnets (x≳0.85) to 〈111〉 ferromagnets (x≲0.85), i.e., with an increasing number of 6d electrons. Namely, the smaller ordered moment in UTe and the gradually decreasing moment in UxTh1−xSb for 1.0⩾x⩾0.3 are attributed to the 6d moments which are polarized antiparallel to the 5f moments.
TL;DR: In this paper, the electronic band structure and partial densities of states of paramagnetic, ferromagnetic and antiferromagnetic ordered FeRh are calculated self-consistently, using the linear muffin-tin orbitals (LMTO) method.
Abstract: The electronic band structure and partial densities of states of paramagnetic, ferromagnetic and antiferromagnetic ordered FeRh are calculated self-consistently, using the linear muffin-tin orbitals (LMTO) method. Comparison is made with other theoretical results and the experimental data. The computer values of the electronic specific heat coefficient and the magnetic moments on each site are in godd agreement with the available calorimetric, magnetisation and neutron diffraction data.
TL;DR: In this paper, a discussion of isotropic magnetic materials with localized magnetic moments between which the exchange interaction is more complex than in the usual Heisenberg model is presented, and experimental data on these materials and their theoretical interpretation are given.
Abstract: This review is primarily devoted to a discussion of isotropic magnetic materials with localized magnetic moments between which the exchange interaction is more complex than in the usual Heisenberg model. They include insulators for which the biquadratic or multispin exchange mechanisms are comparable with the bilinear exchange, conductors which do not satisfy the conditions of validity of the RKKY indirect exchange theory, and the nuclear magnetic material solid helium. Additionally, an analysis is made of high-anisotropy magnetic materials behaving similarly to isotropic non-Heisenberg materials. These anisotropic materials have anomalous properties, compared with the Heisenberg case. Experimental data on these materials and their theoretical interpretation are given. The following topics are discussed: 1) the conditions for a strong non-Heisenberg exchange and non-Heisenberg Hamiltonians; 2) quadrupole ordering and order-proper disorder phase transitions; 3) order-order and order-improper disorder phase transitions; 4) metamagnetism of isotropic materials; 5) normal sequences and "devil's ladders" of phase transitions between commensurable structures; 6) canted antiferromagnetism of high-symmetry crystals which do not obey the condition for the existence of relativistic Dzyaloshinskiĩ-type interactions.
TL;DR: Anomalies were found in electrical conductivity and specific heat at the two-step transition in the stoichiometric YFe2O4. as discussed by the authors concluded that the transition is a new type of Verwey transition: i.e., ordering of ionic charge, Fe2+ and Fe3+, accompanied by lattice distortion and antiferromagnetic spin ordering.
TL;DR: In this article, an ultrasonic measurement was performed on antiferromagnetic MnO for longitudinal and transverse waves propagating along the [100], [110] and [111] directions, from 77 up to 350 K.
TL;DR: In this article, the chromium-ion distribution in xCr2O3-(1−x) [3B 2O3-PbO] glasses with 0⩽x35 mol% Cr2O 3 was studied using X-ray diffraction, EPR and magnetic measurements.
Abstract: By using X-ray diffraction analysis, EPR and magnetic measurements, the chromium-ion distribution in xCr2O3-(1−x) [3B2O3-PbO] glasses with 0⩽x⩽35 mol% Cr2O3 was studied. EPR investigation evidenced the presence of both Cr3+ and Cr5+ ions, the latter being in small proportion, in agreement with the atomic magnetic moment values. For concentrations x⩽20 mol% Cr2O3 the isolated Cr3+ ions coexist with those coupled by super-exchange magnetic interactions, the isolated ones prevailing only for x 20 mol % Cr2O3 microcrystalline precipitates were detected, giving rise to an antiferromagnetic transition with Neel temperature, NN≃310 K and paramagnetic Curie temperature, θp=−480 K.