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Cluster Superconductivity in the Magnetoelectric Pb(Fe_{1/2}Sb_{1/2})O₃ Ceramics

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Laguta V., Marysko M., Stephanovich V., Raevsky I., Olekhnovich N., Pushkarev A., Radyush Y., Raevskaya S., Kuzian R., Chlan V., Štěpánková H.

Acta Physica Polonica A

2017

vol. 131

issue 6

1534-1539

We report the observation of cluster (local) superconductivity in the magnetoelectric Pb(Fe_{1/2}Sb_{1/2})O₃ ceramics prepared at a hydrostatic pressure of 6 GPa and temperatures 1200-1800 K to stabilize the perovskite phase. The superconductivity is manifested by an abrupt drop of the magnetic susceptibility at the critical temperature T_{c} ≈7 K. Both the magnitude of this drop and T_{c} decrease with magnetic field increase. Similarly, the low-field paramagnetic absorption measured by EPR spectrometer drops significantly below T_{c} as well. The observed effects and their critical magnetic field dependence are interpreted as manifestation of the superconductivity and the Meissner effect in metallic Pb nanoclusters existing in the ceramics. Their volume fraction and average size were estimated as 0.1-0.2% and 140-150 nm, respectively. The superconductivity related effects disappear after oxidizing annealing of the ceramics.

Magnetic Properties of the Bi_{0.65}La_{0.35}Fe_{0.5}Sc_{0.5}O₃ Perovskite

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Fedorchenko A., Fertman E., Desnenko V., Kotlyar O., Čižmár E., Shvartsman V., Lupascu D., Salamon S., Wende H., Salak A., Khalyavin D., Olekhnovich N., Pushkarev A., Radyush Y., Feher A.

Acta Physica Polonica A

2017

vol. 131

issue 4

1069-1071

Magnetic properties of polycrystalline multiferroic Bi_{0.65}La_{0.35}Fe_{0.5}Sc_{0.5}O₃ synthesized under high-pressure (6 GPa) and high-temperature (1500 K) conditions were studied using a SQUID magnetometer technique. The temperature dependent static magnetic moment M was measured in both zero-field-cooled and field-cooled modes over the temperature range of 5-300 K in low magnetic field H=0.02 kOe. The field dependent magnetization M(H) was measured in magnetic fields up to 50 kOe at different temperatures up to 230 K after zero-field cooling procedure. A long-range magnetic ordering of the antiferromagnetic type with a weak ferromagnetic contribution takes place below T_{N} ≈ 220 K. Magnetic hysteresis loops taken below T_{N} show a huge coercive field up to H_{c} ≈10 kOe, while the magnetic moment does not saturate up to 50 kOe. A strong effect of magnetic field on the magnetic properties of the compound has been found. Below T_{N} ≈220 K the derivatives of the initial magnetization curves demonstrate the existence of a temperature-dependent anomaly in fields of H=15÷25 kOe. The nature of the anomaly is unknown and requires additional study.

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2 Acta Physica Polonica A

2 2017

2 Olekhnovich N.

2 Pushkarev A.

2 Radyush Y.

1 Chlan V.

1 Desnenko V.

1 Fedorchenko A.

1 Feher A.

1 Fertman E.

1 Khalyavin D.

1 Kotlyar O.

1 Kuzian R.

1 Laguta V.

1 Lupascu D.

1 Marysko M.

1 Raevskaya S.

1 Raevsky I.

1 Salak A.

1 Salamon S.

1 Shvartsman V.

1 Stephanovich V.

1 Wende H.

1 Čižmár E.

1 Štěpánková H.

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Cluster Superconductivity in the Magnetoelectric Pb(Fe_{1/2}Sb_{1/2})O₃ Ceramics

Magnetic Properties of the Bi_{0.65}La_{0.35}Fe_{0.5}Sc_{0.5}O₃ Perovskite