Some layered phyllosilicates are characterized by spontaneous scrolling due to size mismatch between sublayers. The doping of layers by transition metal ions allows nanoscrolls to acquire magnetic properties. The magnetic behavior of synthetic (Mg1 – xCox)3Si2O5(OH)4 (x = 0.2, 0.4, 0.6, 0.8, 1) phyllosilicates with the chrysotile structure before and after partial hydrogen-induced reduction is studied. The dominant ferromagnetic behavior has been revealed in all studied phyllosilicates. Ensembles of cobalt metal nanoparticles in a silicate matrix have demonstrated a collective magnetic response at room temperature with a narrow hysteresis loop and fast saturation.

Ni2CrBO5 has been synthesized and investigated by X-ray diffraction, dc magnetization, and specific heat measurements. The unusual cation distribution has been established: the M1 and M3 sites are occupied by Ni2+ ions, the M2 site is by Cr3+ ions, and the M4 site is mixed, featuring both Ni2+ and Cr3+ ions. The magnetic order onsets at TN = 140 K, which is confirmed by a 7-type peak in specific heat, followed by the dome-shaped anomaly of the magnetization at about 30 K. In the magnetically ordered state, a remarkable sequence of temperature-induced magnetization reversal sensitive to the measurement's regime is observed. Dominant antiferromagnetic interactions are characterized by the Weiss temperature 0 = -73 K. The effective magnetic moment of 5.37 i B per formula unit is close to the spin-only one. The effect of the cation distribution on the magnetic properties is discussed.

A simple and reliable method for determining the critical current of a HTSC tape is a non-contact method based on capturing the magnetic flux by a closed superconducting ring made of this tape and measuring the magnetic field in the center of the ring with a field sensor. This method also makes it possible to obtain the dependence of the critical current on the mag-netic field by applying a magnetic field locally on a small section of the tape. A local magnetic field can be created using strong permanent magnets, which also makes it possible to apply the field at different angles relative to the plane of the tape and to determine the anisotropy of critical currents. Using this method, experiments were carried out on rings made of a SuperOx HTSC tape at T = 77 K and in a magnetic field up to 4 kOe. The values obtained for the anisotropy of critical currents are in good agreement with the data given by the manufacturer.

The magnetization M(H) of the superconducting niobium plate was measured for a series of angles α between the direction of the magnetic field and the plane of the sample. It was found that: 1) M(H) at α = 0° and α = 90° differ significantly; 2) the jumps in the magnetic flux, which are observed on M(H) at low temperatures, also differ significantly for α = 0° and α = 90°; 3) in a wide range of angles, the form of the dependences M(H) and the flux jumps, characteristic of α = 90°, are retained when the magnetic field deviates from the normal of the sample. The same is observed at a deviation from α = 0°, but in a smaller range of angles

The dependence of magnetization M on magnetic field H was measured for a thin superconducting niobium plate with strong magnetic flux pinning with the field oriented normally and parallel to the sample plane. At T < T c , dependences M ( H ) show a hysteretic behavior with a peak effect in large fields; the shape of the hysteresis loop depends on the field orientation. At temperatures below ~ T c /2 magnetic field jumps appear on dependences M ( H ), and their behavior also depends on the field orientation. When a good conductor is in the in a good thermal contact with the planar superconducting sample, the flux jumps are noticeably reduced in the perpendicular field orientation, while the flux jumps in the parallel orientation remain unchanged. The decrease in the magnitude of the flux jumps with a transverse orientation of the magnetic field occurs due to the electrodynamic braking of magnetic instability, which could lead to a magnetic flux jump.

Измерены зависимости намагниченности M от магнитного поля H для сверхпроводящей тонкой ниобиевой пластины с сильным пиннингом магнитного потока при ориентации внешнего поля нормально и параллельно плоскости образца. При T<T c зависимости M(H) имеют гистерезисный характер с пик-эффектом в больших полях, форма петли гистерезиса зависит от ориентации магнитного поля. При температурах ниже ~ T c /2 на зависимостях M(H) появляются скачки магнитного потока, которые по-разному проявляются при различной ориентации магнитного поля. Размещение хорошо проводящего материала в тепловом контакте с плоским сверхпроводящим образцом заметно уменьшает скачки потока в поперечном магнитном поле, в то время как в продольном поле влияния на скачки потока не наблюдается. Уменьшение величины скачков потока при поперечной ориентации магнитного поля происходит из-за электродинамического торможения развития магнитной неустойчивости, приводящей к скачку магнитного потока. Ключевые слова: сверхпроводимость, намагниченность, скачки потока, ниобий, поверхностный барьер, электродинамическое торможение, ориентация магнитного поля.