283 research outputs found

    Optical properties and carrier localization in the layered phosphide EuCd2_\mathbf{2}P2_\mathbf{2}

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    The temperature dependence of the complex optical properties of the layered phosphide material EuCd2_2P2_2 has been measured over a wide frequency range above and below TN11.5T_{\rm N} \simeq 11.5 K for light polarized in the aba-b planes. At room temperature, the optical conductivity is well described by a weak free-carrier component with a Drude plasma frequency of 1100\simeq 1100 cm1^{-1} and a scattering rate of 1/τD7001/\tau_D\simeq 700 cm1^{-1}, with the onset of interband absorptions above 2000\simeq 2000 cm1^{-1}. Two infrared-active EuE_u modes are observed at \simeq\,89 and 239 cm1^{-1}. As the temperature is reduced the scattering rate decreases and the low-frequency conductivity increases slightly; however, below 50\simeq 50 K the conductivity decreases until at the resistivity maximum at 18\simeq 18 K (just below 2TN2T_{\rm N}) the spectral weight associated with free carriers is transferred to a localized excitation at 500\simeq 500 cm1^{-1}. Below TNT_{\rm N}, metallic behavior is recovered. Interestingly, the EuE_u modes are largely unaffected by these changes, with only the position of the high-frequency mode showing any signs of anomalous behavior. While several scenarios are considered, the prevailing view is that the resistivity maximum and subsequent carrier localization is due to the formation of ferromagnetic domains below 2TN\simeq 2T_{\rm N} that result in spin-polarized clusters due to spin-carrier coupling [1].Comment: 8 pages with 6 figures; five pages of supplemental materia

    Pressure Tuned Insulator to Metal Transition in Eu2_2Ir2_2O7_7

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    We have studied the effect of pressure on the pyrochlore iridate Eu2_2Ir2_2O7_7, which at ambient pressure has a thermally driven insulator to metal transition at TMI120T_{MI}\sim120\,K. As a function of pressure the insulating gap closes, apparently continuously, near P6P \sim 6\,GPa. However, rather than TMIT_{MI} going to zero as expected, the insulating ground state crosses over to a metallic state with a negative temperature coefficient of resistivity, calling into question the true nature of both ground states. The high temperature state also crosses over near 6 GPa, from an incoherent to a conventional metal, suggesting a connection between the high and the low temperature states.Comment: 7 pages, 7 figures, updated after publication in Physical Review

    Determining infertility treatment costs and out of pocket payments imposed on couples

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    Background: Infertility and infertility treatment costs are considered as one of the main challenges that human society increasingly face with.Objective: To determine infertility treatment costs and out of pocket expenditures imposed on couples referred to infertility treatment center in Yazd, Iran.Design: A descriptive cross sectional studySubjects: A total of 216 couples were selected and contributed in the study through convenient sampling method.Setting: Telephone interviews with couples and medical documents review were also used to ensure the accuracy of collected information.Results: Lost opportunity, direct and indirect costs were 5.562.526, 37.812.354 and 11.125.395 rial respectively (1USD=33,000 rial). Among direct costs the most and the least expenditures belonged to surgery (24.042.137 rial) and clinical visits (174.053 rial). The greatest portion of indirect costs was related to accommodation expenses and the least was due to travel costs (4.898.099 and 2.738.491 rial). Findings confirmed a significant statistical relation between indirect costs and patients’ living place, also a significant relation between lost opportunity cost and patients’ occupation (P<0.05).Conclusion: Due to the high expenditures related to infertility treatment services also lack of insurance coverage, policy makers should pay a particular attention on meeting the reproductive health needs of a society
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