In Keimer's antiferromagnet, the Higgs mode morphs into different collective-electron motion that resembles particles called Goldstone bosons.
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Keimer aims to actually observe a quantum phase transition in his antiferromagnet, which may be accompanied by additional weird phenomena.
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Cibuc CoGe is an antiferromagnet with a transition temperature Tc of 132 K.
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Nickel(II) thiocyanate, like nickel(II) iodide, nickel(II) bromide and nickel(II) chloride, is an antiferromagnet at low temperatures.
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Copper(II) thiocyanate, like copper(II) bromide and copper(II) chloride, is a quasi low- dimensional antiferromagnet and it orders at 12K into a conventional Néel ground state.
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A soft ferromagnetic film which is strongly exchange-coupled to the antiferromagnet will have its interfacial spins pinned. Reversal of the ferromagnet's moment will have an added energetic cost corresponding to the energy necessary to create a Néel domain wall within the antiferromagnetic film. The added energy term implies a shift in the switching field of the ferromagnet. Thus the magnetization curve of an exchange-biased ferromagnetic film looks like that of the normal ferromagnet except that is shifted away from the H=0 axis by an amount Hb. In most well-studied ferromagnet/antiferromagnet bilayers, the Curie temperature of the ferromagnet is larger than the Néel temperature TN of the antiferromagnet.
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Easy-axis magnetization curves of a) a soft ferromagnetic film; b) an antiferromagnetic film and c) an exchange-biased bilayer consisting of a ferromagnet and an antiferromagnet. The susceptibility (slope) of the antiferromagnetic's magnetization curve is exaggerated for clarity. The essential physics underlying the phenomenon is the exchange interaction between the antiferromagnet and ferromagnet at their interface. Since antiferromagnets have a small or no net magnetization, their spin orientation is only weakly influenced by an externally applied magnetic field.
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Bose–Einstein condensation of magnons was proven in an antiferromagnet at low temperatures by Nikuni et al. and in a ferrimagnet by Demokritov et al. at room temperature. Recently Uchida et al.
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Dipan Ghosh is an Indian theoretical physicist, best known for his exact enumeration of the ground state of a Heisenberg antiferromagnet, known in literature as the Majumdar–Ghosh model, which he developed with Chanchal Kumar Majumdar.
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It is a canonical example of uniaxial antiferromagnet (with Neel temperature of 68 K G.P. Felcher and R. Kleb, Europhys. Lett. 36, 455 (1996)) which has been experimentally studied since early on.J. W. Stout and L. M. Matarrese, Rev. Mod. Phys. 25, 338 (1953).
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High temperature superconductivity appears upon changing the electron density away from a two-dimensional antiferromagnet. Much attention has focused on the intermediate regime between the antiferromagnet and the optimal superconductor, where additional competing orders are found at low temperatures, and a "pseudogap" metal appears in the hole-doped cuprates. Sachdev's theories for the evolution of the competing order with magnetic field, density, and temperature have been successfully compared with experiments. Sachdev and collaborators proposed a sign-problem free Monte Carlo method for studying the onset of antiferromagnetic order in metals: this yields a phase diagram with high temperature superconductivity similar to that found in many materials, and has led to much subsequent work describing the origin of high temperature superconductivity in realistic models of various materials.
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Lanthanum manganite is an electrical insulator and an A-type antiferromagnet. It is the parent compound of several important alloys, often termed rare-earth manganites or colossal magnetoresistance oxides. These families include lanthanum strontium manganite, lanthanum calcium manganite and others. In lanthanum manganite, both the La and the Mn are in the +3 oxidation state.
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Schematic of alternating spin directions in an antiferromagnet. Antiferromagnets, like ferrimagnets, have two sublattices with opposing moments, but now the moments are equal in magnitude. If the moments are exactly opposed, the magnet has no remanence. However, the moments can be tilted (spin canting), resulting in a moment nearly at right angles to the moments of the sublattices.
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Neodymium, a rare-earth metal, was present in the classical mischmetal at a concentration of about 18%. Metallic neodymium has a bright, silvery metallic luster. Neodymium commonly exists in two allotropic forms, with a transformation from a double hexagonal to a body-centered cubic structure taking place at about 863 °C. Neodymium is paramagnetic at room temperature and becomes an antiferromagnet upon cooling to .
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These minerals are strongly magnetic because, at room temperature, they are magnetically ordered (magnetite, maghemite and greigite are ferrimagnets while hematite is a canted antiferromagnet). To relate magnetic measurements to the environment, environmental magnetists have identified a variety of processes that give rise to each magnetic mineral. These include erosion, transport, fossil fuel combustion, and bacterial formation. The latter includes extracellular precipitation and formation of magnetosomes by magnetotactic bacteria.
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Neutron scattering measurements of cesium chlorocuprate Cs2CuCl4, a spin-1/2 antiferromagnet on a triangular lattice, displayed diffuse scattering. This was attributed to spinons arising from a 2D RVB state. Later theoretical work challenged this picture, arguing that all experimental results were instead consequences of 1D spinons confined to individual chains. Afterwards, it was observed in an organic Mott insulator (κ-(BEDT-TTF)2Cu2(CN)3) by Kanoda's group in 2003.
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At a temperature above the ordering point of the magnetic moments, where the material behaves as a paramagnetic one, neutron diffraction will therefore give a picture of the crystallographic structure only. Below the ordering point, e.g. the Néel temperature of an antiferromagnet or the Curie-point of a ferromagnet the neutrons will also experience scattering from the magnetic moments because they themselves possess spin. The intensities of the Bragg reflections will therefore change.
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The simplest kind of magnetic phase is a paramagnet, where each individual spin behaves independently of the rest, just like atoms in an ideal gas. This highly disordered phase is the generic state of magnets at high temperatures, where thermal fluctuations dominate. Upon cooling, the spins will often enter a ferromagnet (or antiferromagnet) phase. In this phase, interactions between the spins cause them to align into large-scale patterns, such as domains, stripes, or checkerboards.
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A QSL is neither a ferromagnet, where magnetic domains are parallel, nor an antiferromagnet, where the magnetic domains are antiparallel; instead, the magnetic domains are randomly oriented. This can be realized e.g. by geometrically frustrated magnetic moments that cannot point uniformly parallel or antiparallel. When cooling down and settling to a state, the domain must "choose" an orientation, but if the possible states are similar in energy, one will be chosen randomly.
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Antiferromagnetic ordering In an antiferromagnet, unlike a ferromagnet, there is a tendency for the intrinsic magnetic moments of neighboring valence electrons to point in opposite directions. When all atoms are arranged in a substance so that each neighbor is anti-parallel, the substance is antiferromagnetic. Antiferromagnets have a zero net magnetic moment, meaning that no field is produced by them. Antiferromagnets are less common compared to the other types of behaviors and are mostly observed at low temperatures.
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Just as all known conventional superconductors are strong phonon systems, all known high-Tc superconductors are strong spin-density wave systems, within close vicinity of a magnetic transition to, for example, an antiferromagnet. When an electron moves in a high-Tc superconductor, its spin creates a spin-density wave around it. This spin-density wave in turn causes a nearby electron to fall into the spin depression created by the first electron (water-bed effect again). Hence, again, a Cooper pair is formed.
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While Philip Anderson had already noted in 1956 the connection between the problem of the frustrated Ising antiferromagnet on a (pyrochlore) lattice of corner-shared tetrahedra and Pauling's water ice problem, real spin ice materials were only discovered forty years later. The first materials identified as spin ices were the pyrochlores Dy2Ti2O7 (dysprosium titanate), Ho2Ti2O7 (holmium titanate). In addition, compelling evidence has been reported that Dy2Sn2O7 (dysprosium stannate) and Ho2Sn2O7 (holmium stannate) are spin ices. These four compounds belong to the family of rare-earth pyrochlore oxides.
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This inequality means that the direction of the exchange bias can be set by cooling through TN in the presence of an applied magnetic field. The moment of the magnetically ordered ferromagnet will apply an effective field to the antiferromagnet as it orders, breaking the symmetry and influencing the formation of domains. The exchange bias effect is attributed to a ferromagnetic unidirectional anisotropy formed at the interface between different magnetic phases. Generally, the process of field cooling from higher temperature is used to obtain ferromagnetic unidirectional anisotropy in different exchange bias systems.
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In condensed matter physics, the quantum dimer magnet state is one in which quantum spins in a magnetic structure entangle to form a singlet state. These entangled spins act as bosons and their excited states (triplons) can undergo Bose-Einstein condensation (BEC). The quantum dimer system was originally proposed by Matsubara and Matsuda as a mapping of the lattice Bose gas to the quantum antiferromagnet. Quantum dimer magnets are often confused as valence bond solids; however, a valence bond solid requires the breaking of translational symmetry and the dimerizing of spins.
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Transition metal atoms often have magnetic moments due to the net spin of electrons that remain unpaired and do not form chemical bonds. In some solids the magnetic moments on different atoms are ordered and can form a ferromagnet, an antiferromagnet or a ferrimagnet. In a ferromagnet—for instance, solid iron—the magnetic moment on each atom is aligned in the same direction (within a magnetic domain). If the domains are also aligned, the solid is a permanent magnet, which is magnetic even in the absence of an external magnetic field.
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The magnetization disappears when the magnet is heated to the Curie point, which for iron is . An antiferromagnet has two networks of equal and opposite magnetic moments, which cancel each other out so that the net magnetization is zero. For example, in nickel(II) oxide (NiO), half the nickel atoms have moments aligned in one direction and half in the opposite direction. In a ferrimagnet, the two networks of magnetic moments are opposite but unequal, so that cancellation is incomplete and there is a non-zero net magnetization.
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The amount of hysteresis shift Hb is not correlated with the density n of uncompensated spins in the plane of the antiferromagnet that appears at the interface. In addition, the exchange bias effect tends to be smaller in epitaxial bilayers than in polycrystalline ones, suggesting an important role for defects. In recent years progress in fundamental understanding has been made via synchrotron radiation based element-specific magnetic linear dichroism experiments that can image antiferromagnetic domains and frequency- dependent magnetic susceptibility measurements that can probe the dynamics. Experiments on the Fe/FeF2 and Fe/MnF2 model systems have been particularly fruitful.
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The presence of local moment and delocalized conduction electrons leads to a competition of the Kondo interaction (which favors a non-magnetic ground state) and the RKKY interaction (which generates magnetically ordered states, typically antiferromagnetic for heavy fermions). By suppressing the Néel temperature of a heavy-fermion antiferromagnet down to zero (e.g. by applying pressure or magnetic field or by changing the material composition), a quantum phase transition can be induced. For several heavy- fermion materials it was shown that such a quantum phase transition can generate very pronounced non-Fermi liquid properties at finite temperatures.
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Lieb-Schultz-Mattis theorem implies that the ground state of the Heisenberg antiferromagnet on a bipartite lattice with isomorphic sublattices, is non-degenerate, i.e., unique, but the gap can be very small.E. Lieb, D. Mattis, Ordering energy levels in interacting spin chains, Journ. Math. Phys. 3, 749–751, (1962) For one-dimensional and quasi-one-dimensional systems of even length and with half-integral spin Affleck and Lieb, generalizing the original result by Lieb, Schultz, and Mattis, proved that the gap \gamma_L in the spectrum above the ground state is bounded above by :\gamma_L\leq c/L, where L is the size of the lattice and c is a constant.
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