We demonstrate a high solubility limit of >9 mol% for MnTe alloying in SnTe. The electrical conductivity of SnTe decreases gradually while the Seebeck coefficient increases remarkably with increasing MnTe content, leading to enhanced power factors. The room-temperature Seebeck coefficients of Mn-doped SnTe are significantly higher than those predicted by theoretical Pisarenko plots for pure SnTe, indicating a modified band structure. The high-temperature Hall data of Sn1–xMnxTe show strong temperature dependence, suggestive of a two-valence-band conduction behavior. Moreover, the peak temperature of the Hall plot of Sn1–xMnxTe shifts toward lower temperature as MnTe content is increased, which is clear evidence of decreased energy separation (band convergence) between the two valence bands. The first-principles electronic structure calculations based on density functional theory also support this point. The higher doping fraction (>9%) of Mn in comparison with ∼3% for Cd and Hg in SnTe gives rise to a muc...

Valence Band Modification and High Thermoelectric Performance in SnTe Heavily Alloyed with MnTe

The present status of theoretical and experimental investigations of solitary excitations in one-dimensional magnetic systems is reviewed. A survey of exact solutions to the nonlinear equations of motion for pertinent classical chain systems (sine-Gordon chain and ferromagnetic Heisenberg chains with various anisotropies) is given. Particular emphasis is devoted to the role of solitons in the thermodynamics of such systems. Models corresponding to real quasi-one-dimensional magnets are broadly discussed to demonstrate the properties of their solitary excitations. The experimental significance of such nonlinear excitations in the static and dynamic quantities of such systems is discussed in detail. The models and model substances are the easy-plane ferromagnet (model substances CsNiF3 and (C6H11NH3)CuBr3), the easy-plane antiferromagnet (CH3)4NMnCl3) and the S = ½ Ising chain with transverse interactions (CsCoCl3). The quantum aspects of solitary excitations are treated in some theoretical detail....

Solitary excitations in one-dimensional magnets

We study the multicritical behavior arising from the competition of two distinct types of ordering characterized by $\mathrm{O}(n)$ symmetries. For this purpose, we consider the renormalization-group flow for the most general $\mathrm{O}{(n}_{1})\ensuremath{\bigoplus}\mathrm{O}{(n}_{2})$-symmetric Landau-Ginzburg-Wilson Hamiltonian involving two fields ${\ensuremath{\varphi}}_{1}$ and ${\ensuremath{\varphi}}_{2}$ with ${n}_{1}$ and ${n}_{2}$ components, respectively. In particular, we determine in which cases, approaching the multicritical point, one may observe the asymptotic enlargement of the symmetry to $\mathrm{O}(N)$ with ${N=n}_{1}{+n}_{2}.$ By performing a five-loop $\ensuremath{\epsilon}$-expansion computation we determine the fixed points and their stability. It turns out that for ${N=n}_{1}{+n}_{2}g~3$ the $\mathrm{O}(N)$-symmetric fixed point is unstable. For $N=3,$ the multicritical behavior is described by the biconal fixed point with critical exponents that are very close to the Heisenberg ones. For $Ng~4$ and any ${n}_{1}{,n}_{2}$ the critical behavior is controlled by the tetracritical decoupled fixed point. We discuss the relevance of these results for some physically interesting systems, in particular for anisotropic antiferromagnets in the presence of a magnetic field and for high-${T}_{c}$ superconductors. Concerning the SO(5) theory of superconductivity, we show that the bicritical O(5) fixed point is unstable with a significant crossover exponent ${\ensuremath{\varphi}}_{4,4}\ensuremath{\approx}0.15;$ this implies that the O(5) symmetry is not effectively realized at the point where the antiferromagnetic and superconducting transition lines meet. The multicritical behavior is either governed by the tetracritical decoupled fixed point or is of first-order type if the system is outside its attraction domain.

https://arxiv.org/pdf/cond-mat/0209580.pdf

Multicritical phenomena in O(n 1 )⊕O(n 2 )-symmetric theories

The manipulation of magnetic ordering with applied electric fields is of pressing interest for new magnetoelectric devices and information storage applications. Recently, such magnetoelectric control was realized in multiferroics. However, their magnetoelectric switching is often accompanied by significant hysteresis, resulting from a large barrier, separating different ferroic states. Hysteresis prevents robust switching, unless the applied field overcomes a certain value (coercive field). Here we address the role of a switching barrier on magnetoelectric control, and identify a material, collinear antiferromagnetic and pyroelectric Ni3TeO6, in which magnetoelectric switching occurs without hysteresis. The barrier between two magnetic states in the vicinity of a spin–flop transition is almost flat, and thus small changes in external electric/magnetic fields allow to switch the ferroic state through an intermediate state in a continuous manner, resulting in a colossal magnetoelectric response. This colossal magnetoelectric effect resembles the large piezoelectric effect at the morphotropic phase boundary in ferroelectrics. Usually magnetoelectric switching is accompanied by hysteresis, which is a consequence of the large barrier between different magnetoelectric states. Here, the authors show that in the antiferromagnet Ni3TeO6magnetoelectric switching of magnetization as well as polarization occur without hysteresis.

/pdf/non-hysteretic-colossal-magnetoelectricity-in-a-collinear-3wbiph5st4.pdf

Non-hysteretic colossal magnetoelectricity in a collinear antiferromagnet

The magnetic state of atomically thin semiconducting layered antiferromagnets such as CrI3 and CrCl3 can be probed by forming tunnel barriers and measuring their resistance as a function of magneti...

Persistence of Magnetism in Atomically Thin MnPS3 Crystals.

In the diluted magnetic semiconductor ${\mathrm{Sn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te the charge-carrier concentration p is of crucial importance for the low-temperature magnetic behavior. By means of neutron-diffraction experiments, in combination with ac-susceptibility, magnetization, and specific-heat data, we show that for x=0.04 the long-range-ordered ferromagnetic state observed for p=7\ifmmode\times\else\texttimes\fi{}${10}^{20}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ gradually evolves into a spin-glass state with increasing carrier concentration. In a crystal with p=11\ifmmode\times\else\texttimes\fi{}${10}^{20}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ initially a transition to a restricted-ranged ferromagnetic order occurs when the temperature is lowered in zero field, followed by a transition to a reentrant spin-glass phase. By the application of a small magnetic field (5.0 mT) the reentrant spin-glass transition is suppressed. In a p=23\ifmmode\times\else\texttimes\fi{}${10}^{20}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ crystal a spin-glass phase is entered directly from the paramagnetic regime. The neutron-diffraction results indicate the presence of short-range ferromagnetic fluctuations in this sample. The results are discussed in the context of a Ruderman-Kittel-Kasuya-Yosida model. A three-dimensional (T,x,p) magnetic phase diagram is presented.

Neutron-diffraction study of the carrier-concentration-induced ferromagnet-to-spin-glass transition in the diluted magnetic semiconductor Sn 1 − x Mn x Te

The short- and long-range spin correlations in the quasi-one-dimensional S=(1/2) system (C6D11ND3)CuBr3 (CHAB-D14) have been investigated by (quasi) elastic neutron scattering experiments. The temperature dependence of the sublattice magnetization below TN=1.56 K reflects the presence of ferromagnetic chains in this compound. The intrachain spin correlations in the paramagnetic region show a crossover from isotropic Heisenberg behavior at high temperatures to XY behavior below ~3 K, and are surprisingly well described by a classical spin model.

/pdf/short-and-long-range-correlations-in-the-s-1-2-ferromagnetic-2t1uoh88g0.pdf

Short- and long-range correlations in the S=1/2 ferromagnetic chain system (C6D11ND3)CuBr3.

The behavior of the orthorhombic, weakly anisotropic antiferromagnet CsMn${\mathrm{Br}}_{3}$ \ifmmode\cdot\else\textperiodcentered\fi{} 2${\mathrm{D}}_{2}$O in a magnetic field applied along the easy axis, was investigated by means of neutron scattering. By observing the intensities of several magnetic Bragg reflections a rather complete picture of the field and temperature dependence of the staggered magnetization ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{M}}}_{\mathrm{st}}$ was obtained. The data on ${M}_{\mathrm{st}}^{\ensuremath{\parallel}}(H, T)$ and ${M}_{\mathrm{st}}^{\ensuremath{\perp}}(H, T)$, the order parameters of the antiferromagnetic and the spin-flop phase, respectively, allow several direct experimental tests of the extended-scaling theory for bicritical behavior. From the vanishing of the order parameters the paramagnetic phase boundaries ${T}_{c}^{\ensuremath{\parallel}}(H)$ and ${T}_{c}^{\ensuremath{\perp}}(H)$ were determined. The location of the first-order spin-flop line ${H}_{\mathrm{SF}}(T)$ in the ($H, T$) diagram could be derived from the reorientation of ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{M}}}_{\mathrm{st}}$ at this transition. Although the present compound is known as a pseudo-one-dimensional Heisenberg system, the shape of the phase boundaries is well described by the extended-scaling theory. The observed crossover exponent $\ensuremath{\varphi}$ is in fair agreement with the theoretical prediction for an orthorhombic spin-flop system. However, the fitted slope $q$ of the optimum $t=0$ scaling axis strongly deviates from Fisher's estimate, which probably is not valid for a low-dimensional system. The data also provide a more direct confirmation of the central postulate of the extended-scaling theory. In order to test the validity of this scaling hypothesis, two different procedures for the scaling of the data are employed, and plots are constructed in which all scaled data points accumulate onto the two alternative bicritical scaling functions $\mathcal{W}$ or $\mathcal{m}$. In these plots the anticipated symmetry between the ${M}_{\mathrm{st}}^{\ensuremath{\parallel}}$ and ${M}_{\mathrm{st}}^{\ensuremath{\perp}}$ data is striking. In $\mathcal{m}$ the crossover from bicritical to critical behavior can be observed clearly. As a result of the different data analyses, the following "best values" for the various parameters might be indicated: ${T}_{b}=5.255(5)$ K, ${H}_{b}=26.55(2)$ kOe, $q=5.5(2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ kOe, $w=6.3(4)\ifmmode\times\else\texttimes\fi{}{10}^{3}$ k${\mathrm{Oe}}^{2}$, $\ensuremath{\varphi}=1.18(3)$, ${\ensuremath{\beta}}_{b}=0.33(2)$, ${\ensuremath{\beta}}_{\ensuremath{\parallel}}=0.321(4)$, and ${\ensuremath{\beta}}_{\ensuremath{\perp}}=0.326(6)$. The critical exponents ${\ensuremath{\beta}}_{\ensuremath{\parallel}}$ and ${\ensuremath{\beta}}_{\ensuremath{\perp}}$ are in good agreement with the theoretical $d=3$ Ising value. Also the observed bicritical exponents ${\ensuremath{\beta}}_{b}$ and $\ensuremath{\varphi}$ agree with the theoretical $d=3$ $\mathrm{XY}$ values.

Neutron-scattering study of bicritical behavior in CsMn Br 3 · 2 D 2 O

In the weakly anisotropic antiferromagnet Co${\mathrm{Br}}_{2}$ \ifmmode\cdot\else\textperiodcentered\fi{} 6(0.48${\mathrm{D}}_{2}$O, 0.52${\mathrm{H}}_{2}$O) the reorientation of the sublattice magnetizations from antiferromagnetic (AF) to spin-flop (SF) ordering has been studied by neutron scattering and magnetization measurements. Strong evidence has been obtained for the existence of an intermediate phase between the AF and SF phase, which persists up to a tetracritical point.

Intermediate phase in the spin-flop system Co Br 2 · 6(0.48 D 2 O, 0.52 H 2 O)

The crystal structure of (Zn 1− x Mn x ) 3 As 2 has been determined with neutron powder diffraction for x = 0, 0.08 and 0.135. The structure of these compounds turned out to be the same as that of the α-phase of Cd 3 As 2 , space group I4 1 cd. The diffraction for a sample with nominal x = 0.2 indicates the presence of several phases.

E. Frikkee

Papers

Neutron-diffraction study of the carrier-concentration-induced ferromagnet-to-spin-glass transition in the diluted magnetic semiconductor Sn 1 − x Mn x Te

Short- and long-range correlations in the S=1/2 ferromagnetic chain system (C6D11ND3)CuBr3.

Neutron-scattering study of bicritical behavior in CsMn Br 3 · 2 D 2 O

Intermediate phase in the spin-flop system Co Br 2 · 6(0.48 D 2 O, 0.52 H 2 O)

The crystal structure of the diluted magnetic semiconductor zinc manganese arsenide (Zn1-xMnx)3As2)