V. A. Suetin

Investigation of the behaviour of the impurity atoms in Si by μ−SR-method

The dependence of the residual polarization of negative muons in p-type Si on temperature in the 4.2–270 K range has been investigated. Measurements were carried out in external magnetic field of 0.08 T transverse to the muon spin. The impurity concentration in the sample was 2 · 1013 cm−3. Muon spin relaxation was observed at temperatures below 30 K. The relaxation rate atT=30 K is equal to 0.18±0.08μs−1. The relaxation rate grows with the decrease of temperature and at 4.2 K exceeds 30μs−1. The value of the residual polarization at zero timeP(t=0) is constant within the investigated temperature range.In the rangeT<30 K data on the relaxation rate are well described by the dependence λ=B·T−q, whereq=2.75. Power dependence of Λ may evidence the essential role of the phonon mechanism in the relaxation of the electron momentum of the acceptor center.

Magnetism in disordered magnetic Fe82−xNixCr18

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.

μSR study of antiferromagnetic phase-transitions in dysprosium and holmium

It is shown that the temperature dependence Λ (T) of the muon spin relaxation rate in the paramagnetic state of dysprosium and holmium does not reveal any singularity at T−>TN′ where TN is the Neel temperature. This result contradicts the assumption of the second-order antiferromagnetic phase-transition in these metals and is in good agreement with computations within the renormalization group method.

Study of local magnetic fields in the oxide α-Bi2O3 byNQR andμSR techniques

NQR andμSR investigations of the local magnetic field inα-Bi2O3 were performed. In theNQR experiments onα-Bi2O3 which is usually considered as diamagnetic, the splitting of the spectral lines revealed a local field on the bismuth nuclei. The internal magnetic field obtained byμSR significantly exceeds the dipole field from Bi nuclear magnetic moments. A possible source of the local magnetic fields is partial covalent bonds inα-Bi2O3.

The MSR-investigation of antiferromagnetic phase transitions in erbium

The muon spin relaxation rateΛ (T) in an orientated polycrystalline sample of erbium constructed of large monocrystals has been measured for temperatures 20 <T<300 K. It has been shown that theΛ (T) for erbium is bounded from above asT → TN, whereTN=84.4 K is the Néel temperature. This fact may be explained by assuming that atT=TN erbium undergoes a weak phase-transition of the first order.

The μSR investigations on the phasotron at Dubna: The present and the future

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 μSR study of the relaxation of Ho and Er magnetic moments in high-Tc 1-2-3 compounds

High temperature superconductors HoBa2Cu3O7−δ (Tc ≅93 K), Ho0.5Y0.5Ba2Cu3O7−δ (Tc≅93 K) and ErBa2Cu3O7−δ (Tc≅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.

Penetration depth and pinning effects in high-Tc superconductors La-Sr-Cu-O and (Er, Ho)-Ba-Cu-O studies by μSR

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.

μSR study of Cu10Zr7

It is shown that temperature dependences Λ(T) of dipole relaxation rate of the positive muon spin in crystalline and amorphous states of Cu10Zr7 are approximately the same over the temperature interval 20–300 K. this fact points out approximately identical close-order structure of crystalline and amorphous states of Cu10Zr7 alloy.

Quantum diffusion of muons in bismuth

A muon spin relaxation rate in a super-pure sample of bismuth has been measured. The experimental data and the theory of coherent diffusion in crystalline lattices with shifted levels are compared.