Spin - Phonon Coupling in Nickel Oxide Determined from Ultraviolet Raman Spectroscopy

Nickel oxide (NiO) has been studied extensively for various applications ranging from electrochemistry to solar cells [1,2]. In recent years, NiO attracted much attention as an antiferromagnetic (AF) insulator material for spintronic devices [3-10]. Understanding the spin - phonon coupling in NiO is a key to its functionalization, and enabling AF spintronics' promise of ultra-high-speed and low-power dissipation [11,12]. However, despite its status as an exemplary AF insulator and a benchmark material for the study of correlated electron systems, little is known about the spin - phonon interaction, and the associated energy dissipation channel, in NiO. In addition, there is a long-standing controversy over the large discrepancies between the experimental and theoretical values for the electron, phonon, and magnon energies in NiO [13-23]. This gap in knowledge is explained by NiO optical selection rules, high Neel temperature and dominance of the magnon band in the visible Raman spectrum, which precludes a conventional approach for investigating such interaction. Here we show that by using ultraviolet (UV) Raman spectroscopy one can extract the spin - phonon coupling coefficients in NiO. We established that unlike in other materials, the spins of Ni atoms interact more strongly with the longitudinal optical (LO) phonons than with the transverse optical (TO) phonons, and produce opposite effects on the phonon energies. The peculiarities of the spin - phonon coupling are consistent with the trends given by density functional theory calculations. The obtained results shed light on the nature of the spin - phonon coupling in AF insulators and may help in developing innovative spintronic devices.Comment: 16 pages; 2 figure

Intra-Landau level Cyclotron Resonance in Bilayer Graphene

Interaction driven integer quantum Hall effects are anticipated in graphene bilayers because of the near-degeneracy of the eight Landau levels which appear near the neutral system Fermi level. We predict that an intra-Landau-level cyclotron resonance signal will appear at some odd-integer filling factors, accompanied by collective modes which are nearly gapless and have approximate $k^{3/2}$ dispersion. We speculate on the possibility of unususal localization physics associated with these modes.Comment: 5 pages, 2 figure

The Impact of Parenting on First-Time Mothers Mental Health and Sense of Competence: A Mixed-Method Study

Early adverse childhood experiences impact the psychosocial functioning of individuals when they become parents themselves including links to postnatal mental health problems. Previous research primarily focused broadly on attachments styles or the impact of abuse on parenting. This mixed-method study will look at both negative and positive day-to-day parenting interactions that mothers experienced with their own parents. A community sample of 212 first time mothers of infants under 12-months old completed questionnaires relating to perceptions of being parented, parenting stress, parenting sense of competence, postnatal depression and postnatal anxiety. 25 of these mothers were then interviewed 1:1 to explore at a deeper level the transition to motherhood and aspects of their own parenting that they draw upon. Quantitative data was analysed using PROCESS for moderating and mediating relationships and qualitative data was analysed using reflexive thematic analysis. Results showed that both positive and negative experiences of being parented affect mothers’ sense of competence and that this relationship is mediated by mental health disorders such as depression and anxiety. Stress moderated some of these relationships. Reflexive thematic analysis generated themes explaining how mothers’ made sense of and responded to their own experiences of being parented in order to manage their own mental health and develop their own parenting styles. These findings have implications for postnatal mental health services and parenting programs