A cascade of magnetic phase transitions and a 1/3-magnetization plateau in selenite-selenate Co3(SeO3)(SeO4)(OH)2 with kagomé-like Co2+ ion layer arrangements: the importance of identifying a correct spin lattice

We prepared a new compound, Co₃(SeO₃)(SeO₄)(OH)₂, having layers in a kagomé-like arrangement of Co²⁺ (spin S = 3/2) ions. This phase crystallizes in the orthorhombic space group Pnma (62) with unit cell parameters a = 11.225(9) Å, b = 6.466(7) Å and c = 11.530(20) Å. Its layers, parallel to the ab-plane, are made up of Co1O₅ square pyramids and Co2O₆ and Co3O₆ octahedra. As the temperature is lowered, Co₃(SeO₃)(SeO₄)(OH)₂ undergoes three successive magnetic transitions at 27.5, 19.4 and 8.1 K, and the magnetization of Co₃(SeO₃)(SeO₄)(OH)₂ measured at 2.4 K exhibits a 1/3-magnetization plateau between 7.8 and 19.9 T. The H-T magnetic phase diagram constructed for Co₃(SeO₃)(SeO₄)(OH)₂ from ac and dc magnetic susceptibility, specific heat and magnetization measurements contains three magnetic phases I, II and III. Phase I is antiferromagnetic, while phases II and III are ferrimagnetic and responsible for the 1/3-magnetization plateau. To interpret these complex magnetic properties, we identified the correct spin lattice for Co₃(SeO₃)(SeO₄)(OH)₂ by evaluating its intralayer and interlayer spin exchanges based on spin-polarized DFT+U calculations.

Observation of a 1/3 magnetization plateau in Pb2Cu10O4(SeO3)4Cl7 arising from (Cu2+)7 clusters of corner-sharing (Cu2+)4 tetrahedra

A mixed-valence compound Pb₂Cu₁₀O₄(SeO₃)₄Cl₇ has a complex structure consisting of one nonmagnetic Cu⁺ (S = 0) ion and four nonequivalent magnetic Cu²⁺ (S = 1/2) ions. It exhibits antiferromagnetic ordering at T_N = 10.2 K. At a temperature below T_N, a sequence of spin-flop transition at B_spin-flop = 1.3 T and 1/3 plateau formation at B_spin-flip = 4.4 K is observed in the magnetization curve M(B). The 1/3 magnetization plateau persists at least up to 53.5 T. The spin exchanges of Pb₂Cu₁₀O₄(SeO₃)₄Cl₇ evaluated by performing energy-mapping analysis based on DFT+U calculations show that the magnetic properties of Pb₂Cu₁₀O₄(SeO₃)₄Cl₇ are described by the (Cu²⁺)₇ cluster of corner-sharing (Cu²⁺)₄ tetrahedra, and that each (Cu²⁺)₇ cluster has a S = 3/2 spin arrangement in the ground state. The 1/3 magnetization plateau observed for Pb₂Cu₁₀O₄(SeO₃)₄Cl₇ is explained by the field-induced flip of every second (Cu²⁺)₇ cluster within a unit cell.

Magnetism of coupled spin tetrahedra in ilinskite-type KCu5O2(SeO3)2Cl3

Synthesis, thermodynamic properties, and microscopic magnetic model of ilinskite-type KCu5O2(SeO3)2Cl3 built by corner-sharing Cu4 tetrahedra are reported, and relevant magnetostructural correlations are discussed. Quasi-one-dimensional magnetic behavior with the short-range order around 50 K is rationalized in terms of weakly coupled spin ladders (tubes) having a complex topology formed upon fragmentation of the tetrahedral network. This fragmentation is rooted in the non-trivial effect of the SeO3 groups that render the Cu-O-Cu superexchange strongly ferromagnetic even at bridging angles exceeding 110°.

[Ultrasonic methods of diagnosis of late complications after reconstructive surgery of the aorta and major arteries of the lower limbs]

Long-standing results were studied in 587 patients who sustained reconstructive vascular surgeries when aged under 16 years (the average age was 6 years and 4 months). Out of them 141 patients faced the necessity of repeated surgeries: in 115 (81.6%) patients the extremity function was preserved, in 19 (13.5%) a repeated amputation was performed, 7 patients (4.9%) expired. All those operated on had been actively followed up with the use of periodical instrumental investigation which included dopplerography and ultrasonic angiography. High significance of ultrasonic technique was proved as the use of it permitted one to detect late complications on the early stages of their development and perform surgical corrections before the development of life-threatening complications. Therefore repeated preventive surgeries were performed in 53 patients, 52 of them were a success. Repeated amputations were performed in 1 patient. All those operated on survived.

[Characteristics of blood flow in the vertebral arteries in scalenus anticus syndrome]

The authors studied hemodynamics in the vertebral arteries in 62 patients with the scalenus-anticus syndrome by means of radioconstrast angiography and ultrasonic angiography which produced a colour image of the vessels with calculation of the diameter and the linear and volume blood flow rate. The results of the study showed that in constriction of the subclavian artery to 60% of its diameter in the typical place, the volume blood flow rate in the vertebral arteries remained normal (184 +/- 6.9 ml/min) but reduced 1.5-2 times during the functional test. Adequate surgical correction restored normal hemodynamics, control ultrasonic angiography recorded increase of the volume blood flow rate in the vertebral values to normal values. Ultrasonic angiography provides authentic information on the character of affection of the subclavian artery in the scalenus-anticus syndrome and makes it possible to appraise the hemodynamic significance of affection of the vertebral arteries. Besides, the method allows objective evaluation of the efficacy of treatment and quantitative characteristics of hemodynamics.

[Ultrasonic angiography in the diagnosis of occlusive diseases of major arteries of the legs]

A positive feature of non-invasive ultrasonic angiography is thought by the authors to be its high informative value. A generalized experience with 657 examinations performed in 285 patients is presented.