High temperature superconductors HoBa2Cu3O7−δ (T c ≅93 K), Ho0.5Y0.5Ba2Cu3O7−δ (T c ≅93 K) and ErBa2Cu3O7−δ (T c ≅95 K) were investigated by the zero-field μSR-technique. The muon spin depolarisation rate connected with the fluctuation frequency of rare-earth ion magnetic moments was measured. It was found that the samples with holmium show a fast increase of the muon spin depolarisation rate at temperatures below 20 K, while in ErBa2Cu3O7−δ the depolarisation rate remains low in the whole temperature region studied (4.2 K-270 K). The sharp difference between the behaviours of the muon spin depolarisation rate may be explained by the difference between the ground state of Ho3+ and Er3+ ions in the crystalline field of the lattice.
Памяти Аркадия Бенедиктовича Мигдала, Беляев С.Т., Вакс В.Г., Гуревич И.И., Коган В.И., Ларкин А.И., Окунь Л.Б., Понтекорво Б.М., Саперштейн Э.Е., Скринский А.Н., Суетин В.А., Трубников Б.А., Халатников И.М., Ходель В.А.
The zero field μSR-method has been used to study the magnetism in the disordered magnetic alloy Fe82−xNixCr18 near the three-critical, pointx=25. The dynamic and static local field distributions are analyzed. The difference between spin-glass states obtained either from the paramagnetic or after the double transition is discussed.
After conversion of the LNP JINR phasotron new opportunities have been opened for μSR-research. A new round of investigations has begun since 1987. In this paper we present the summary of the results achieved and give some prospects for future investigations.
The substitution of the trivalent Y for the bivalent Ca in Bi2Sr2Ca1−xYxCu2O8+δ changes the charge carrier density in this compound. We have performed the muon spin rotation measurements of the London penetration depth λ(T) in the high-Tc superconductor Bi2Sr2Ca1−xYxCu2O8+δ for x=0.0−0.45. The yttrium doping leads to a decrease in Tc and to an increase in λ(0). In all investigated samples the penetration depth revealed the temperature dependence which can be explained within the framework of conventional BCS theory in the weak coupling limit.
We report the results of μSR investigations of the ceramic samples La2-xSrxCuO4-σ (x=0.1, 0.15, 0.25) and ReBa2Cu3O7-σ (Re=Er, Ho, Y0.5Ho0.5) in the external magnetic field 0–800 Oe. The measurements were performed by the ZFC and FC methods. The irreversibility effects were studied at several temperatures by measuring the mean value and the width of the magnetic field distribution on the muon in the step by step procedure of increasing and subsequent decreasing of the external field. The temperature dependences of the magnetic penetration depth perpendicular to the basal plane λ⊥ were obtained. For the lanthanum sample with 0.15 of Sr its value at the zero temperature is λ⊥ (0)=2400 Å, for Er-Ba-Cu-O λ⊥ (0)=1600 Å.
Zero field muon spin relaxation measurements of the ceramic high-Tc superconductors HoBa2Cu3O7-σ, Oc≃93 K) and ErBa2Cu3O7-σ (Tc≃95 K) reveal the sharp difference between the behaviours of the muon spin relaxation rate at temperatures below 20K. This fact may be explained by assumption that the frequency of fluctuations of Er magnetic moments exceeds by far the fluctuation frequency of Ho in 1-2-3 compounds.
The ceramical system La2-xSrx CuO4 was investigated in the temperature range 4.4–270 K. At the concentrations of Sr x=0.0 and 0.01 the formation of the antiferromagnetic state was observed. The results of the investigations of the magnetic ordering in the fluctuating formation region are given. Investigation of the sample with x=0.07 at the temperature T < 13K confirmed the existence of the spin glass state. The values of the magnetic penetration depth at different temperatures for the superconducting samples are given. The influence of the pinning on the magnetic field distribution in the mixed state of the superconductor is discussed.