Boehnke, Alexander: Tunnel magneto-Seebeck effect: improving the effect size ; spintronics and spincaloritronics. 2016
Inhalt
- 1 Introduction
- 2 Theoretical background
- 2.1 Tunnel magnetoresistance
- 2.2 Charge Seebeck effect
- 2.3 Tunnel magneto-Seebeck effect
- 2.3.1 The TMS in the free electron model
- 2.3.2 Thermoelectricty in the Landauer-Büttiker formalism
- 2.3.3 Linearized Landauer-Büttiker formalism
- 2.3.4 The linearized and nonlinearized formalism
- 2.3.5 The transmission and the chemical potential
- 2.3.6 The transmission and the density of states
- 2.4 Enhancing the tunnel magneto-Seebeck effect
- 3 Methods & Materials
- 3.1 Tunnel magneto-Seebeck effect setup
- 3.1.1 Optical setup
- 3.1.2 Connecting the sample to the measurement electronics
- 3.1.3 Tunnel magnetoresistance in the optical setup
- 3.1.4 Tunnel magneto-Seebeck voltage
- 3.1.5 Temporal evolution of the Seebeck voltage
- 3.1.6 Tunnel magneto-Seebeck current
- 3.1.7 Seebeck effect under applied bias voltage
- 3.2 Fabrication of magnetic tunnel junctions
- 3.3 X-ray analysis
- 3.4 Finite element simulations
- 4 Results
- 4.1 Typical TMS measurements with laser heating
- 4.2 Temperatures in the MTJs
- 4.3 Tunnel magneto-Seebeck effect under applied bias voltage
- 4.4 High tunnel magneto-Seebeck effect in Heusler compounds
- 5 Conclusion & Outlook
- Appendix
- A Linearization of the Landauer formula
- B Leakage current through the voltage amplifier
- C Tunnel magneto-Seebeck effect under bias voltage
- C.1 Direct and indirect determination of the Seebeck voltages
- C.2 Peltier and Thomson effects
- C.3 Bias enhanced TMS effect at a second MTJ
- C.4 Contributions from the bias voltage and Seebeck voltage
- D Further TMS data of Heusler based MTJs
- E Cryostat insert for Seebeck and Nernst experiments
- Publications
- Conferences & Talks
- Acknowledgments
- Bibliography