Magnetic Study of the Low-Temperature Anomalies in the Optimally Doped PrBCO Compound
The anomalous magnetic properties of a nonsuperconducting PrBa<sub>2</sub>Cu<sub>3</sub>O<sub>6+</sub> <inline-formula><tex-math notation="LaTeX">$_{x}$</tex-math></inline-formula> (or PrBCO) compound in an optimally doped oxygen state of concentration (<inline-formula><tex-math notation="LaTeX">$x= {\text{0.95}}$</tex-math> </inline-formula>) are investigated at low temperatures using magnetic measurements such paraprocess magnetic susceptibility <inline-formula><tex-math notation="LaTeX">$\chi _{{\text{H}}}(T)$</tex-math></inline-formula> under different values of a DC magnetic field <italic>H</italic> up to 8 T and isothermal magnetizations <inline-formula> <tex-math notation="LaTeX">$M_{{\text{T}}}(H)$</tex-math></inline-formula> with <italic>H</italic> up to 2.1 T. The temperature dependences of the derivatives of <inline-formula><tex-math notation="LaTeX">$\chi _{{\text{H}}}(T)$ </tex-math></inline-formula> indicate a significant decrease with increasing <italic>H</italic> of the Néel temperature <inline-formula><tex-math notation="LaTeX">$T_{{\text{N}}}= {\text{14}}\,{\text{K}}$</tex-math> </inline-formula> associated with antiferromagnetic (AFM) Pr ordering. The AFM-paramagnetic phase transition remains well defined even at 8 T, whereas the small anomaly at <inline-formula><tex-math notation="LaTeX">$T_{2}= {\text{10.5}}\,{\text{K}}$</tex-math></inline-formula>, which is due to the spin reorientation phase transition already reported before, seems clearly highlighted at 2 T but entirely suppressed above 6 T. A weak ferromagnetic (WFM) contribution is revealed below <inline-formula><tex-math notation="LaTeX">$T_{{\text{N}}}$</tex-math> </inline-formula> with more evidence particularly below the low critical point <inline-formula> <tex-math notation="LaTeX">$T_{{\text{cr}}}= {\text{4-5 K}}$</tex-math></inline-formula> whose anomaly is still visible with increasing <italic>H</italic> up to 8 T. Weak field-induced transitions between AFM and WFM phases are observed in the derivatives of <inline-formula><tex-math notation="LaTeX">$M_{{\text{T}}}(H)$</tex-math></inline-formula> at a low transition field (<inline-formula><tex-math notation="LaTeX">$H_{{\text{t}}}< {\text{1}}\,{\text{T}}$</tex-math> </inline-formula>). All results are discussed and compared with those found in previous works.
Magnetic order of Pr in PrBa2Cu3O7.
The magnetic order of Pr in nonsuperconducting PrBa{sub 2}Cu{sub 3}O{sub 7} has been studied by specific-heat, susceptibility, and neutron-diffraction measurements. The basic ordering consists of a simple antiferromagnetic arrangement, with a saturated moment of 0.24{mu}{sub {ital B}} and a Neel temperature {ital T}{sub {ital N}} of {similar to}17 K, which is two orders of magnitude higher than expected from either dipolar or Rudeman-Kittel-Kasuya-Yosida interactions alone. The small moment, along with the large value of the low-temperature electronic specific-heat coefficient {gamma} of 196 mJ/mol K{sup 2}, suggests that there is substantial {ital f}-electron character at the Fermi level.
5.63 and 5.80 MeV levels of Ne20; de-excitation branching
Abstract The ratio Г γ /Г for the 5.63 and 5.80 MeV levels of Ne 20 has been determined to be 0.077 (±0.008) and −4 , respectively, by using the C 12 (C 12 , α)Ne 20 reaction and determining the fraction of the events in which the alpha-particle and the Ne 20 recoil are present in coincidence at the kinematically correct angles. In both cases these results in themselves are shown to imply radiative E1 transition (5.63→1.63 and 5.80→0, respectively) probabilities ⪡5 × 10 −5 Weisskopf units. When taken together with the life-time for the 5.63 MeV level measured by Evans et al . values of Г( E1 ) ≲ 5 × 10 −6 and Г α ≈ 6% of the particle estimate are obtained for this state.