ترغب بنشر مسار تعليمي؟ اضغط هنا

Single crystal growth and physical properties of pyroxene CoGeO$_3$

88   0   0.0 ( 0 )
 نشر من قبل Alexander Christoph Komarek
 تاريخ النشر 2021
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

We report on the synthesis and physical properties of cm-sized CoGeO$_3$ single crystals grown in a high pressure mirror furnace at pressures of 80~bar. Direction dependent magnetic susceptibility measurements on our single crystals reveal highly anisotropic magnetic properties that we attribute to the impact of strong single ion anisotropy appearing in this system with T$_N$~$sim$~33.5~K. Furthermore, we observe effective magnetic moments that are exceeding the spin only values of the Co ions which reveals the presence of sizable orbital moments in CoGeO$_3$.



قيم البحث

اقرأ أيضاً

106 - H. Guo , L. Zhao , M. Baenitz 2021
Despite the absence of an apparent triangular pattern in the crystal structure, we observe unusually well pronounced 1/3 magnetization plateaus in the quasi one-dimensional Ising spin chain compound CoGeO$_3$ which belongs to the class of pyroxene mi nerals. We succeeded in uncovering the detailed microscopic spin structure of the 1/3 magnetization plateau phase by means of neutron diffraction. We observed changes of the initial antiferromagnetic zero-field spin structure that are resembling a regular formation of antiferromagnetic domain wall boundaries, resulting in a kind of modulated magnetic structure with 1/3-integer propagation vector. The net ferromagnetic moment emerges at these domain walls whereas two third of all antiferromagnetic chain alignments can be still preserved. We propose a microscopic model on the basis of an anisotropic frustrated square lattice to explain the observations.
65 - Yong Liu , Tao Ma , Lin Zhou 2019
We report on the crystal and magnetic structures, magnetic, and transport properties of SrMnSb$_2$ single crystals grown by the self-flux method. Magnetic susceptibility measurements reveal an antiferromagnetic (AFM) transition at $T_{rm N} = 295(3)$ K. Above $T_{rm N}$, the susceptibility slightly increases and forms a broad peak at $T sim 420$ K, which is a typical feature of two-dimensional magnetic systems. Neutron diffraction measurements on single crystals confirm the previously reported C-type AFM structure below $T_{rm N}$. Both de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) effects are observed in SrMnSb$_2$ single crystals. Analysis of the oscillatory component by a Fourier transform shows that the prominent frequencies obtained by the two different techniques are practically the same within error regardless of sample size or saturated magnetic moment. Transmission electron microscopy (TEM) reveals the existence of stacking faults in the crystals, which result from a horizontal shift of Sb atomic layers suggesting possible ordering of Sb vacancies in the crystals. Increase of temperature in susceptibility measurements leads to the formation of a strong peak at $T sim {570}$ K that upon cooling under magnetic field the susceptibility shows a ferromagnetic transition at $T_{rm C} sim 580$ K. Neutron powder diffraction on crushed single-crystals does not support an FM phase above $T_{rm N}$. Furthermore, X-ray magnetic circular dichroism (XMCD) measurements of a single crystal at the $L_{2,3}$ edge of Mn shows a signal due to induced canting of AFM moments by the applied magnetic field. All evidence strongly suggests that a chemical transformation at the surface of single crystals occurs above 500 K concurrently producing a minute amount of ferromagnetic impurity phase.
108 - Yogesh Singh , Y. Lee , S. Nandi 2008
Single crystals of BaRh_2As_2 have been synthesized from a Pb flux. We present the room temperature crystal structure, single crystal x-ray diffraction measurements as a function of temperature T, anisotropic magnetic susceptibility chi versus T, ele ctrical resistivity in the ab-plane rho versus T, Hall coefficient versus T and magnetic field H, and heat capacity C versus T measurements on the crystals. The single crystal structure determination confirms that BaRh_2As_2 forms in the tetragonal ThCr_2Si_2 type structure (space group I4/mmm) with lattice parameters a = b = 4.0564(6)AA and c = 12.797(4) AA. Band structure calculations show that BaRh_2As_2 should be metallic with a small density of states at the Fermi energy N(E_ F) = 3.49 states/eV f.u. (where f.u. equiv formula unit) for both spin directions. rho(T) data in the ab-plane confirm that the material is indeed metallic with a residual resistivity rho(2K) = 29 mu Omega cm, and with a residual resistivity ratio rho(310K)/rho(2K) = 5.3. The observed chi(T) is small (sim 10^{-5} cm^3/mol) and weakly anisotropic with chi_{ab}/chi_ c approx 2. The C(T) data indicate a small density of states at the Fermi energy with the low temperature Sommerfeld coefficient gamma = 4.7(9) mJ/mol K^2. There are no indications of superconductivity, spin density wave, or structural transitions between 2K and 300K. We compare the calculated density of states versus energy of BaRh_2As_2 with that of BaFe_2As_2.
We report on the crystal structure, magnetic susceptibility, specific heat, electrical and thermoelectrical properties of AmPd5Al2, the americium counterpart of the unconventional superconductor NpPd5Al2. AmPd5Al2 crystallizes in the ZrNi2Al5-type of structure with lattice parameters: a = 4.1298 A and c = 14.7925 A. Magnetic measurements of AmPd5Al2 indicate a paramagnetic behavior with no hint of magnetic ordering nor superconductivity down to 2 K. This aspect is directly related to its 5f6 electronic configuration with J = 0. The specific heat measurements confirm the non magnetic ground state of this compound. The low temperature electronic specific heat gamma_el = 20 mJ mol-1K-2 is clearly enhanced as compared to americium metal. All transport measurements obtained point to a metallic behavior in AmPd5Al2.
We have grown the new uranium compound URhIn$_5$ with the tetragonal HoCoGa$_5$-type by the In self flux method. In contrast to the nonmagnetic ground state of the isoelectronic analogue URhGa$_5$, URhIn$_5$ is an antiferromagnet with antiferromagnet ic transition temperature $T_{rm N}$ = 98 K. The moderately large electronic specific heat coefficient $gamma$ = 50 mJ/K$^2$mol demonstrates the contribution of 5$f$ electrons to the conduction band. On the other hand, magnetic susceptibility in the paramagnetic state roughly follows a Curie-Weiss law with a paramagnetic effective moment corresponding to a localized uranium ion. The crossover from localized to itinerant character at low temperature may occur around the characteristic temperature 150 K where the magnetic susceptibility and electrical resistivity show a marked anomaly.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا