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Register a new userMagnetism of the antiferromagnetic spin-$frac{1}{2}$ tetramer compound CuInVO$_5$
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We measured the temperature dependence of the magnetic susceptibility and specific heat and the magnetic-field dependence of the magnetization of CuInVO$_5$. An antiferromagnetically ordered state appears below $T_{rm N} = 2.7$ K. We observed a $frac{1}{2}$ quantum magnetization plateau above 30 T at 1.3 K. We show that the spin system consists of antiferromagnetic spin-$frac{1}{2}$ tetramers with $J_1 = 240 pm 20$ and $J_2 = -142 pm 10$ K for the intratetramer interactions.
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We measured magnetization, specific heat, electron spin resonance, neutron diffraction, and inelastic neutron scattering of CrVMoO$_7$ powder. An antiferromagnetically ordered state appears below $T_{rm N} = 26.5 pm 0.8$ K. We consider that the probable spin model for CrVMoO$_7$ is an interacting antiferromagnetic spin-$frac{3}{2}$ dimer model. We evaluated the intradimer interaction $J$ to be $25 pm 1$ K and the effective interdimer interaction $J_{rm eff}$ to be $8.8 pm 1$ K. CrVMoO$_7$ is a rare spin dimer compound that shows an antiferromagnetically ordered state at atmospheric pressure and zero magnetic field. The magnitude of ordered moments is $0.73(2) mu_{rm B}$. It is much smaller than a classical value $sim 3 mu_{rm B}$. Longitudinal-mode magnetic excitations may be observable in single crystalline CrVMoO$_7$.
Here, we report the synthesis and magnetic properties of a Yb-based triangular-lattice compound LiYbS$_2$. At low temperatures, it features an effective spin-$frac{1}{2}$ state due to the combined effect of crystal electric field and spin orbit coupling. Magnetic susceptibility measurements and $^7$Li nuclear magnetic resonance experiments reveal the absence of magnetic long range ordering down to 2~K, which suggests a possible quantum spin liquid ground state. A dominant antiferromagnetic nearest neighbour exchange interaction $J/k_{rm B}simeq$ 5.3~K could be extracted form the magnetic susceptibility. The NMR linewidth analysis yields the coupling constant between the Li nuclei and Yb$^{3+}$ ions which was found to be purely dipolar in nature.
We report zero and longitudinal magnetic field muon spin relaxation measurements of the spin S=1/2 antiferromagnetic Heisenberg chain material SrCuO2. We find that in a weak applied magnetic field B the spin-lattice relaxation rate follows a power law B^n with n=-0.9(3). This result is temperature independent for 5K < T < 300 K. Within conformal field theory and using the Muller ansatz we conclude ballistic spin transport in SrCuO2.
Single crystals of a metal organic complex ce{(C5H12N)CuBr3} (ce{C5H12N} = piperidinium, pipH for short) have been synthesized and the structure was determined by single-crystal X-ray diffraction. ce{(pipH)CuBr3} crystallizes in the monoclinic group $C$2/$c$. Edging-sharing ce{CuBr5} units link to form zigzag chains along the $c$ axis and the neighboring Cu(II) ions with spin-1/2 are bridged by bi-bromide ions. Magnetic susceptibility data down to 1.8 K can be well fitted by the Bonner-Fisher formula for antiferromagnetic spin-1/2 chain, giving the intrachain magnetic coupling constant $J$ $sim$ 17 K. At zero field, ce{(pipH)CuBr3} shows three-dimensional (3D) order below $T_N$ = 1.68 K. Calculated by the mean-field theory, the interchain coupling constant $J$ = 0.65 K is obtained and the ordered magnetic moment $m_0$ is about 0.20 $mu_B$. This value of $m_0$ makes ce{(pipH)CuBr3} a rare compound suitable to study the dimensional crossover problem in magnetism, since both 3D order and one-dimensional (1D) quantum fluctuations are prominent. In addition, specific heat measurements reveal two successive magnetic transitions with lowering temperature when external field $H geq$ 3 T is applied along the $a$ axis. The $H$ - $T$ phase diagram of ce{(pipH)CuBr3} is roughly constructed. The interplay between exchange interactions, dimensionality, Zeeman energy and possible Dzyaloshinkii-Moriya interaction should be the driving force for the multiple phase transitions.
The zero-temperature quantum phase diagram of the spin-$frac{1}{2}$ $J_{1}$--$J_{2}$--$J_{1}^{perp}$ model on an $AA$-stacked bilayer honeycomb lattice is investigated using the coupled cluster method (CCM). The model comprises two monolayers in each of which the spins, residing on honeycomb-lattice sites, interact via both nearest-neighbor (NN) and frustrating next-nearest-neighbor isotropic antiferromagnetic (AFM) Heisenberg exchange iteractions, with respective strengths $J_{1} > 0$ and $J_{2} equiv kappa J_{1}>0$. The two layers are coupled via a comparable Heisenberg exchange interaction between NN interlayer pairs, with a strength $J_{1}^{perp} equiv delta J_{1}$. The complete phase boundaries of two quasiclassical collinear AFM phases, namely the N{e}el and N{e}el-II phases, are calculated in the $kappa delta$ half-plane with $kappa > 0$. Whereas on each monolayer in the N{e}el state all NN pairs of spins are antiparallel, in the N{e}el-II state NN pairs of spins on zigzag chains along one of the three equivalent honeycomb-lattice directions are antiparallel, while NN interchain spins are parallel. We calculate directly in the thermodynamic (infinite-lattice) limit both the magnetic order parameter $M$ and the excitation energy $Delta$ from the $s^{z}_{T}=0$ ground state to the lowest-lying $|s^{z}_{T}|=1$ excited state (where $s^{z}_{T}$ is the total $z$ component of spin for the system as a whole, and where the collinear ordering lies along the $z$ direction) for both quasiclassical states used (separately) as the CCM model state, on top of which the multispin quantum correlations are then calculated to high orders ($n leq 10$) in a systematic series of approximations involving $n$-spin clusters. The sole approximation made is then to extrapolate the sequences of $n$th-order results for $M$ and $Delta$ to the exact limit, $n to infty$.
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