Electronic and Magnetic Reconstructions in Manganite Superlattices

We investigate the electronic reconstruction at the interface between ferromagnetic metallic (FM) and antiferromagnetic insulating (AFI) manganites in superlattices using a two-orbital double-exchange model including superexchange interactions, Jahn-Teller lattice distortions, and long range Coulomb interactions. The magnetic and the transport properties critically depend on the thickness of the AFI layers. We focus on superlattices where the constituent parent manganites have the same electron density n = 0.6. The induced ferromagnetic moment in the AFI layers decreases monotonically with increasing layer width, and the electron-density profile and the magnetic structure in the center of the AFI layer gradually return to the bulk limit. The width of the AFI layers and the charge-transfer profile at the interfaces control the magnitude of the magnetoresistance and the metal-insulator transition of the FM/AFI superlattices.Comment: 11 pages, 10 figure

Interfacial Magnetism in Manganite Superlattices

We use a two-orbital double-exchange model including Jahn-Teller lattice distortions, superexchange interactions, and long-range Coulomb (LRC) interactions to investigate the origin of magnetically disordered interfaces between ferromagnetic metallic (FM) and antiferromagnetic insulating (AFI) manganites in FM/AFI superlattices. The induced magnetic moment in the AFI layer varies non-monotonically with increasing AFI layer width as seen in the experiment. We provide a framework for understanding this non-monotonic behavior which has a one-to-one correspondence with the magnetization of the FM interface. The obtained insights provide a basis for improving the tunneling magnetoresistance in FM/AFI manganite superlattices by avoiding a magnetic dead layer (MDL) in the FM manganite.Comment: 5 pages, 5 figures. To appear in PR

Assessing Service Quality in the Ghanaian Private Healthcare Sector: The Case of Comboni Hospital.

The healthcare industry has become a paramount concern for most people in Ghana and the quality of services rendered to the patients in the private hospitals cannot be overemphasized. Patients need quality of services most and are willing to seek better services. The government has been the main provider of health care services in Ghana but recently, some Non-Governmental Organization’s (NGO’s), private individuals and stakeholders also provide health care services which has surged the competitiveness in creating more healthcare facilities in Ghana. This study seeks to explore patients' choice of selecting quality healthcare services and the factors that affect patient satisfaction in private hospitals using the case of Comboni Hospital in Sogakope, Ghana. The study therefore used the quantitative research method to collect the data and SPSS version 22 was used to analyze the data on high-quality healthcare. The SERVQUAL model was used as the measurement scale. Multiple regression analysis was used to reveal the effect of the independent variables (reliability, responsiveness, empathy, assurance, and tangibility) on the dependent variable (patient satisfaction). A detailed description in the analysis and the data processing identified the main factors affecting the general perceptions and patient preferences about their healthcare in the private hospital. The study revealed that there exist a positive result and perception for quality healthcare services without a negative expectation of the patient healthcare being compromised. The study recommends that both the government and the private agencies should consider the important aspects of the hospital’s healthcare management and also the policy and decision makers should have an efficient and effective standard that impact the quality of healthcare assessment in Ghana

Towards Cogenesis via Asymmetric Freeze-in: The χ\chi Who Came-in from the Cold

In models of freeze-in the dark matter (DM) is decoupled from the visible sector and initially has a depleted number density. The hidden and visible sectors are connected only via a feeble portal interaction by which DM can be produced. Asymmetric freeze-in (AFI) combines this scenario with ideas from asymmetric DM and provides a potential cogenesis mechanism. However, it has been argued that existing AFI models do not produce suitably large particle asymmetries due to cancellations which arises because the mediator state remains in thermal equilibrium. We examine AFI via an out-of-equilibrium mediator and using a simple scalar model show that in this case sizeable asymmetries may be generated.Comment: 18 page

Urban Fathers Asset Building – Final Report

The Urban Fathers Asset Building (UFAB) project demonstrated the potential benefits, as well as limitations, of an innovative nexus between the child support system, fatherhood programs, and the Assets for Independence (AFI) grant-funded services. UFAB was a collaborative initiative of the Texas Office of the Attorney General (OAG), Baylor College of Medicine’s Teen Health Clinic, Covenant Community Capital Corporation (the local AFI grantee), and RAISE Texas, the statewide association of AFI grantees. This Final Report summarizes UFAB’s operational features and outcomes; depicts the demonstration’s challenges and innovative responses; reviews the accomplishments of the ancillary projects supported by BAFF funds; and assesses the prospects for sustaining demonstration practices in the Houston area, as well as extending promising practices to other areas of the state.Texas Office of the Attorney GeneralRay Marshall Center for the Study of Human Resource

Electronic Structure and Phase Transition in V2O3: Importance of 3d Spin-Orbit Interaction and Lattice Distortion

The 3d electronic structure and phase transition in pure and Cr doped V2O3 are theoretically investigated in relation to the 3d spin-orbit interaction and lattice distortion. A model consisting of the nearest-neighbor V ion pair with full degeneracy of the 3d orbitals is studied within the many-body point of view. It is shown that each V ion with S=1 spin state has a large orbital magnetic moment $\sim 0.7 \mu_{\rm B}$ and no orbital ordering occurs in the antiferromagnetic insulating (AFI) phase. The anomalous resonant Bragg reflection found in the AFI phase is attributed to the magnetic ordering. In the AFI and paramagnetic insulating (PI) phases, Jahn-Teller like lattice instability leads to tilting of the V ion pairs from the corundum c-axis and this causes large difference in the orbital occupation between the paramagnetic metal and the insulating phases, which is consistent with linear dichroic V 2p XAS measurements. To understand the AFI to PI transition, a model spin Hamiltonian is also proposed. The transition is found to be simultaneous order-disorder transition of the magnetic moments and tilting directions of the V ion pairs. Softening of elastic constant C44 and abrupt change in short range spin correlations observed at the transition are also explained.Comment: 18 pages, 16 figure

Phase Separation in A-site Ordered Perovskite Manganite LaBaMn2_2O6_6 Probed by 139^{139}La and 55^{55}Mn NMR

$^{139}$La- and $^{55}$Mn-NMR spectra demonstrate that the ground state of the A-site ordered perovskite manganite LaBaMn$_2$O$_6$ is a spatial mixture of the ferromagnetic (FM) and antiferromagnetic (AFI(CE)) regions, which are assigned to the metallic and the insulating charge ordered state, respectively. This exotic coexisting state appears below 200 K via a first-order-like formation of the AFI(CE) state inside the FM one. Mn spin-spin relaxation rate indicates that the FM region coexisting with the AFI(CE) one in LaBaMn$_2$O$_6$ is identical to the bulk FM phase of the disordered form La$_{0.5}$Ba$_{0.5}$MnO$_3$ in spite of the absence of A-site disorder. This suggests mesoscopic rather than nanoscopic nature of FM region in LaBaMn$_2$O$_6$\@.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Let