اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدLow temperature magnetic properties of NpNi$_5$
116
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We present the result of an extended experimental characterization of the hexagonal intermetallic Haucke compound NpNi$_{5}$. By combining macroscopic and shell-specific techniques, we determine the 5$f$-shell occupation number $n_f$ close to 4 for the Np ions, together with orbital and spin components of the ordered moment in the ferromagnetic phase below T$_C$ = 16 K ($mu_{S}$ = -1.88~$mu_{B}$ and $mu_{L}$ = 3.91~$mu_{B}$). The apparent coexistence of ordered and disordered phases observed in the M{o}ssbauer spectra is explained in terms of slow relaxation between the components of a quasi-triplet ground state. The ratio between the expectation value of the magnetic dipole operator and the spin magnetic moment ($3langle T_{z}rangle/ langle S_{z}rangle$ = +1.43) is positive and large, suggesting a localized character of the 5$f$ electrons. The angular part of the spin-orbit coupling ($langlevec{ell}cdotvec{s}rangle$ = -5.55) is close to the value of -6.25 calculated for trivalent Np ions in intermediate coupling approximation. The results are discussed against the prediction of first-principle electronic structure calculations based on the spin-polarized local spin density approximation plus Hubbard interaction, and of a mean field model taking into account crystal field and exchange interactions.
قيم البحث
اقرأ أيضاً
A comprehensive experimental and theoretical study of the low temperature properties of GdCoIn$_5$ was performed. Specific heat, thermal expansion, magnetization and electrical resistivity were measured in good quality single crystals down to $^4$He
temperatures. All the experiments show a second-order-like phase transition at 30 K probably associated with the onset of antiferromagnetic order. Total energy GGA+U calculations indicate a ground state with magnetic moments localized at the Gd ions and allowed a determination of the Gd-Gd magnetic interactions. Band structure calculations of the electron and phonon contributions to the specific heat and Quantum Monte Carlo calculations of the magnetic contributions to the thermodynamic quantities reproduce quite well the experimental data.
We present magnetic susceptibility, heat capacity, and neutron diffraction measurements of polycrystalline Nd2Ru2O7 down to 0.4 K. Three anomalies in the magnetic susceptibility measurements at 146, 21 and 1.8 K are associated with an antiferromagnet
ic ordering of the Ru4+ moments, a weak ferromagnetic signal attributed to a canting of the Ru4+ and Nd3+ moments, and a long-range-ordering of the Nd3+ moments, respectively. The long-range order of the Nd3+ moments was observed in all the measurements, indicating that the ground state of the compound is not a spin glass. The magnetic entropy of Rln2 accumulated up to 5 K, suggests the Nd3+ has a doublet ground state. Lattice distortions accompany the transitions, as revealed by neutron diffraction measurements, and in agreement with earlier synchrotron x-ray studies. The magnetic moment of the Nd3+ ion at 0.4 K is estimated to be 1.54(2){mu}B and the magnetic structure is all-in all-out as determined by our neutron diffraction measurements.
Temperature-dependent reflectivity measurements on the kagome metal CsV$_3$Sb$_5$ in a broad frequency range of $50-20000$ cm$^{-1}$ down to $T$=10 K are reported. The charge-density wave (CDW) formed below $T_{rm CDW}$ = 94 K manifests itself in a p
rominent spectral-weight transfer from low to higher energy regions. The CDW gap of 60-75 meV is observed at the lowest temperature and shows significant deviations from an isotropic BCS-type mean-field behavior. Absorption peaks appear at frequencies as low as 200 cm$^{-1}$ and can be identified with interband transitions according to density-functional calculations. The change in the interband absorption compared to KV$_3$Sb$_5$ reflects the inversion of band saddle points between the K and Cs compounds. Additionally, a broader and strongly temperature-dependent absorption feature is observed below 1000 cm$^{-1}$ and assigned to a displaced Drude peak. It reflects localization effects on charge carriers.
The crystal structure and magnetic properties of YCo$_5$ compound have been studied by neutron diffraction, in the pressure range $0 le p le 7.2 GPa$. The experimental data are analyzed together with results from the combined Density Functional and
Dynamical Mean-Field Theory. A good agreement between the experimentally determined and calculated values of cobalt moments is shown. Our scenario for the behavior of YCo$_5$ under pressure, is the combined action of the Lifshitz transition with a strong local electron-electron interaction.
We report the low-temperature properties of SrNd$_2$O$_4$, a geometrically frustrated magnet. Magnetisation and heat capacity measurements performed on polycrystalline samples indicate the appearance of a magnetically ordered state at $T_{rm N}=2.28(
4)$~K. Powder neutron diffraction measurements reveal that an afm state with the propagation vector QV is stabilised below this temperature. The magnetic order is incomplete, as only one of the two Nd$^{3+}$ sites carries a significant magnetic moment while the other site remains largely disordered. The presence of a disordered magnetic component below $T_{rm N}$ is confirmed with polarised neutron diffraction measurements. In an applied magnetic field, the bulk properties measurements indicate a phase transition at about 30~kOe. We construct a tentative $H$-$T$ phase diagram of sno from these measurements.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
