Changes and factors in mental health functioning of adolescents in therapy : a thesis presented in partial fulfilment of the requirements for the degree of Master of Arts in Psychology at Massey University (Palmerston North), New Zealand

Appendix D is not availableTo explore factors that might contribute to changes in mental health functioning in adolescents with mental health problems seen at a Child, Adolescent, and Family Mental Health Service (CAFMHS), the present study examined changes in scores on the Clinical Outcomes of Routine Evaluation (CORE) and the Health of the Nation Outcome Scales for Children and Adolescents (HoNOSCA) over a 3 month period. Ten female and 5 male adolescents completed the CORE and 7 of their respective therapists assessed their mental health on HoNOSCA, before and after 3 months of intervention. Life events and factors within therapy during the period of the study were assessed through interviews with clients and their respective therapists. Analysis of the data indicated that overall the mental health of the participants did improve. No significant correlations between clients' and clinicians' assessment of therapeutic factors were found. The hypotheses that focused on factors that might have contributed to the changes were not supported, possibly due to the small number of participants. Limitations of the study and future directions were discussed

Graphene-WS2_2 heterostructures for tunable spin injection and spin transport

We report the first measurements of spin injection in to graphene through a 20 nm thick tungsten disulphide (WS$_2$) layer, along with a modified spin relaxation time ({\tau}s) in graphene in the WS$_2$ environment, via spin-valve and Hanle spin-precession measurements, respectively. First, during the spin-injection into graphene through a WS$_2$-graphene interface, we can tune the interface resistance at different current bias and modify the spin injection efficiency, in a correlation with the conductivity-mismatch theory. Temperature assisted tunneling is identified as a dominant mechanism for the charge transport across the interface. Second, we measure the spin transport in graphene, underneath the WS$_2$ crystal and observe a significant reduction in the {\tau}s down to 17 ps in graphene in the WS$_2$ covered region, compared to that in its pristine state. The reduced {\tau}s indicates the WS$_2$-proximity induced additional dephasing of the spins in graphene.Comment: 7 Pages, 6 figure

Electrical spin injection, transport, and detection in graphene-hexagonal boron nitride van der Waals heterostructures: progress and perspectives

The current research in graphene spintronics strives for achieving a long spin lifetime, and efficient spin injection and detection in graphene. In this article, we review how hexagonal boron nitride (hBN) has evolved as a crucial substrate, as an encapsulation layer, and as a tunnel barrier for manipulation and control of spin lifetimes and spin injection/detection polarizations in graphene spin valve devices. First, we give an overview of the challenges due to conventional SiO$_2$ substrate for spin transport in graphene followed by the progress made in hBN based graphene heterostructures. Then we discuss in detail the shortcomings and developments in using conventional oxide tunnel barriers for spin injection into graphene followed by introducing the recent advancements in using the crystalline single/bi/tri-layer hBN tunnel barriers for an improved spin injection and detection which also can facilitate two-terminal spin valve and Hanle measurements, at room temperature, and are of technological importance. A special case of bias induced spin polarization of contacts with exfoliated and chemical vapour deposition (CVD) grown hBN tunnel barriers is also discussed. Further, we give our perspectives on utilizing graphene-hBN heterostructures for future developments in graphene spintronics.Comment: Review, Author submitted manuscript - draft; 25 pages, 8 figure

Spin current induced magnetization oscillations in a paramagnetic disc

When electron spins are injected uniformly into a paramagnetic disc, they can precess along the demagnetizing field induced by the resulting magnetic moment. Normally this precession damps out by virtue of the spin relaxation which is present in paramagnetic materials. We propose a new mechanism to excite a steady-state form of this dynamics by injecting a constant spin current into this paramagnetic disc. We show that the rotating magnetic field generated by the eddy currents provide a torque which makes this possible. Unlike the ferromagnetic equivalent, the spin-torque-oscillator, the oscillation frequency is fixed and determined by the dimensions and intrinsic parameters of the paramagnet. The system possesses an intrinsic threshold for spin injection which needs to be overcome before steady-state precession is possible. The additional application of a magnetic field lowers this threshold. We discuss the feasibility of this effect in modern materials. Transient analysis using pump-probe techniques should give insight in the physical processes which accompany this effect

Verification of the Thomson-Onsager reciprocity relation for spin caloritronics

We investigate the Thomson-Onsager relation between the spin-dependent Seebeck and spin-dependent Peltier effect. To maintain identical device and measurement conditions we measure both effects in a single Ni$_{80}$Fe$_{20}$/Cu/Ni$_{80}$Fe$_{20}$ nanopillar spin valve device subjected to either an electrical or a thermal bias. In the low bias regime, we observe similar spin signals as well as background responses, as required by the Onsager reciprocity relation. However, at large biases, deviation from reciprocity occurs due to dominant nonlinear contribution of the temperature dependent transport coefficients. By systematic modeling of these nonlinear thermoelectric effects and measuring higher order thermoelectric responses for different applied biases, we identify the transition between the two regimes as the point at which Joule heating start to dominate over Peltier heating. Our results signify the importance of local equilibrium for the validity of this phenomenological reciprocity relation.Comment: 5 pages, 5 figure