Temperature and field dependence of the phase separation, structure, and magnetic ordering in La1−x_{1-x}Cax_xMnO3_3, (x=0.47x=0.47, 0.50, and 0.53)

Neutron powder diffraction measurements, combined with magnetization and resistivity data, have been carried out in the doped perovskite La$_{1-x}$Ca$_x$MnO$_3$ ($x=0.47$, 0.50, and 0.53) to elucidate the structural, magnetic, and electronic properties of the system around the composition corresponding to an equal number of Mn3+ and Mn4+. At room temperature all three samples are paramagnetic and single phase, with crystallographic symmetry Pnma. The samples then all become ferromagnetic (FM) at $T_C\approx 265$ K. At $\sim 230$ K, however, a second distinct crystallographic phase (denoted A-II) begins to form. Initially the intrinsic widths of the peaks are quite large, but they narrow as the temperature decreases and the phase fraction increases, indicating microscopic coexistence. The fraction of the sample that exhibits the A-II phase increases with decreasing temperature and also increases with increasing Ca doping, but the transition never goes to completion to the lowest temperatures measured (5 K) and the two phases therefore coexist in this temperature-composition regime. Phase A-II orders antiferromagnetically (AFM) below a N\'{e}el temperature $T_N \approx 160$ K, with the CE-type magnetic structure. Resistivity measurements show that this phase is a conductor, while the CE phase is insulating. Application of magnetic fields up to 9 T progressively inhibits the formation of the A-II phase, but this suppression is path dependent, being much stronger for example if the sample is field-cooled compared to zero-field cooling and then applying the field. The H-T phase diagram obtained from the diffraction measurements is in good agreement with the results of magnetization and resistivity.Comment: 12 pages, 3 tables, 11 figure

Independent freezing of charge and spin dynamics in La1.5Sr0.5CoO4

We present elastic and quasielastic neutron scattering measurements characterizing peculiar short-range charge-orbital and spin order in the layered perovskite material La1.5Sr0.5CoO4. We find that below Tc~750 K holes introduced by Sr doping lose mobility and enter a statically ordered {\it charge glass} phase with loosely correlated checkerboard arrangement of empty and occupied d{3z2-r2} orbitals (Co3+ and Co2+). The dynamics of the resultant mixed spin system is governed by the anisotropic nature of the crystal-field Hamiltonian and the peculiar exchange pattern produced by the orbital order. It undergoes a {\it spin freezing} transition at much a lower temperature, Ts~30 K.Comment: 4 pages, 3 figures, Latex. Submitted to PR

Magnetic properties of the S=1/2 quasi-one-dimensional antiferromagnet CaCu2O3

We report single crystal growth and magnetic susceptibility and neutron diffraction studies of the S=1/2 quasi-1D antiferromagnet CaCu2O3. The structure of this material is similar to that of the prototype two-leg spin-ladder compound SrCu2O3. However, the Cu-O-Cu bond angle in the ladder rungs in CaCu2O3 is equal to 123 deg, and therefore the magnetic interaction along the rungs is expected to be much weaker in this material. At high temperatures, the magnetic susceptibility of CaCu2O3 can be decomposed into a contribution from 1D antiferromagnetic chains of finite-size chain segments together with a weak Curie contribution. The intrachain magnetic exchange constant, determined from the magnetic susceptibility measurements, is 2000 K. CaCu2O3 undergoes a Neel transition at T_N=25 K with ordering wavevector of (0.429(5), 0.5, 0.5). The magnetic structure is incommensurate in the direction of the frustrated interchain interaction. Weak commensurate (0.5, 0.5, 0.5) magnetic peaks are also observed below T_N. Application of a magnetic field induces a metamagnetic transition at which the incommensurability of the magnetic structure is substantially reduced. The material possesses only short-range magnetic order above the transition field.Comment: 12 pages, 10 embedded figure

Paul and Onesimus

Recent investigations into the law of fugitives and suppliants in hellenistic Egypt, a law which was based upon the procedure of classic Greece and so was generally like hellenistic law throughout the east, have thrown much light upon the subject, and suggest a reconsideration of the case, of Onesimus and his relations with Paul and Philemon. According to the law of Athens a slave whose life was in danger might flee to an altar and claim sanctuary. The first altar available was frequently the hearth of some private family, with its associations of the family religion. If a refugee rushed into the house and claimed sanctuary, the householder was under legal obligations to give him protection, at least temporarily, while following one of two possible courses. Either he must reconcile the slave to going back to the master, probably by giving the wretch some assurance that the master's wrath was mollified, or, if the slave persisted in refusing to trust himself with the master, the householder was obliged to put the slave up for sale in the market, and pay to the slave's owner the price received. The latter alternative was fraught with serious possibilities for the slave, since in a sale of this kind the circumstances would prejudice prospective buyers against him, and he would probably be purchased only for the roughest sort of service, such as the galleys or the mines. Rather than face such an uncertainty the slave would certainly be glad to go back to the first master if there were any reasonable hope of clemency.</jats:p

Jewish symbols in the Greco - Roman period : V.10.: Symbolism in The Dura Synagogue

New Yorkxi, 251 p.; 31 c

Jewish symbols in the Greco - Roman period : V.12.: Summary and conclusions

New Yorkxii, 217 p.; 31 c

Jewish symbols in the Greco - Roman period : V.9.: Symbolism in The Dura Synagogue

New Yorkxvii, 237 p.; 31 c

Jewish symbols in the Greco - Roman period : V.11.: Symbolism in The Dura Synagogue

New Yorkxv, 21 plt, 354 p.; 31 c

Jewish symbols in the Greco - Roman period : V.13.: Indexes and maps

Princetonvii, 240 p.; 31 c