اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدSpin gap behavior in Cu$_2$Sc$_2$Ge$_4$O$_{13}$ by $^{45}$Sc nuclear magnetic resonance
102
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We report the results of a $^{45}$Sc nuclear magnetic resonance (NMR) study on the quasi-one-dimensional compound Cu$_2$Sc$_2$Ge$_4$O$_{13}$ at temperatures between 4 and 300 K. This material has been a subject of current interest due to indications of spin gap behavior. The temperature-dependent NMR shift exhibits a character of low-dimensional magnetism with a negative broad maximum at $T_{max}$ $simeq $ 170 K. Below $% T_{max}$, the NMR shifts and spin lattice relaxation rates clearly indicate activated responses, confirming the existence of a spin gap in Cu$_2$Sc$_2$Ge% $_4$O$_{13}$. The experimental NMR data can be well fitted to the spin dimer model, yielding a spin gap value of about 275 K which is close to the 25 meV peak found in the inelastic neutron scattering measurement. A detailed analysis further points out that the nearly isolated dimer picture is proper for the understanding of spin gap nature in Cu$_2$Sc$_2$Ge$_4$O$_{13}$.
قيم البحث
اقرأ أيضاً
Cu$_2$Fe$_2$Ge$_4$O$_{13}$ is a bicomponent compound that consists of Cu dimers and Fe chains with separate energy scale. By inelastic neutron scattering technique with high-energy resolution we observed the indirect Fe - Fe exchange coupling by way
of the Cu dimers. The obtained parameters of the effective indirect interaction and related superexchange interactions are consistent with those estimated semi-statically. The consistency reveals that the Cu dimers play the role of nonmagnetic media in the indirect magnetic interaction.
We study $S=1/2$ dimer excitation in a coupled chain and dimer compound Cu$_2$Fe$_2$Ge$_4$O$_{13} by inelastic neutron scattering technique. The Zeeman split of the dimer triplet by a staggered field is observed at low temperature. With the increase
of temperature the effect of random field is detected by a drastic broadening of the triplet excitation. Basic dynamics of dimer in the staggered and random fields are experimentally identified in Cu$_2$Fe$_2$Ge$_4$O$_{13}.
The unusual magnetic properties of a novel low-dimensional quantum ferrimagnet Cu$_2$Fe$_2$Ge$_4$O$_{13}$ are studied using bulk methods, neutron diffraction and inelastic neutron scattering. It is shown that this material can be described in terms o
f two low-dimensional quantum spin subsystems, one gapped and the other gapless, characterized by two distinct energy scales. Long-range magnetic ordering observed at low temperatures is a cooperative phenomenon caused by weak coupling of these two spin networks.
Magnetic excitations of the recently discovered frustrated spin-1/2 two-leg ladder system Li$_2$Cu$_2$O(SO$_4$)$_2$ are investigated using inelastic neutron scattering, magnetic susceptibility and infrared absorption measurements. Despite the presenc
e of a magnetic dimerization concomitant with the tetragonal-to-triclinic structural distortion occurring below 125 K, neutron scattering experiments reveal the presence of dispersive triplet excitations above a spin gap of $Delta = 10.6$ meV at 1.5 K, a value consistent with the estimates extracted from magnetic susceptibility. The likely detection of these spin excitations in infrared spectroscopy is explained by invoking a dynamic Dzyaloshinskii-Moriya mechanism in which light is coupled to the dimer singlet-to-triplet transition through an optical phonon. These results are qualitatively explained by exact diagonalization and higher-order perturbation calculations carried out on the basis of the dimerized spin Hamiltonian derived from first-principles.
We present nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements performed on single crystalline ccag{}, a member of a recently discovered family of heavy fermion materials Ce$_2M$Al$_7$Ge$_4$ ($M$ = Co, Ir, Ni, or Pd).
Previous measurements indicated a strong Kondo interaction as well as magnetic order below $T_M = 1.8$ K. Our NMR spectral measurements show that the Knight shift $K$ is proportional to the bulk magnetic susceptibility $chi$ at high temperatures. A clear Knight shift anomaly ($K otpropto chi$) is observed at coherence temperatures $T^* sim 17.5$ K for $H_0 parallel hat{c}$ and 10 K for $H_0 parallel hat{a}$ at the ${}^{59}$Co site, and $T^* sim 12.5$ K at the ${}^{27}$Al(3) site for $H_0 parallel hat{a}$ characteristic of the heavy fermion nature of this compound. At high temperatures the ${}^{59}$Co NMR spin-lattice relaxation rate $T_1^{-1}$ is dominated by spin fluctuations of the 4$f$ local moments with a weak metallic background. The spin fluctuations probed by ${}^{59}$Co NMR are anisotropic and larger in the basal plane than in the $c$ direction. Furthermore, we find $(T_1TK)^{-1} propto T^{-1/2}$ at the ${}^{59}$Co site as expected for a Kondo system for $T > T^*$ and $T> T_K$. ${}^{59}$Co NQR slrr{} measurements at low temperatures indicate slowing down of spin fluctuations above the magnetic ordering temperature $T_M sim 1.8$ K. A weak ferromagnetic character of fluctuations around $mathbf{q}=0$ is evidenced by an increase of $chi T$ versus $T$ above the magnetic ordering temperature. We also find good agreement between the observed and calculated electric field gradients at all observed sites.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
