George C. HadjipanayisDepartment of Physics and Astronomy Sharp Lab, University of Delaware, Newark, Delaware 19716
Permanent magnets (PMs) are indispensable for the electric, electronic and automobile industries, information technologies, automatic control engineering and many other commercial and military applications. In most of these applications, an increase in the magnetic energy density of the PM, usually presented via the maximum energy product (BH)max, immediately increases the efficiency of the whole device and makes it smaller and lighter. Worldwide demand for high performance PMs has increased substantially in the past few years driven by hybrid and electric cars, wind turbines and other power generation systems.
A dramatic improvement in the performance of PMs was made during the 20th century, with (BH)max increased by more than 100 times, as a result of major advances in solid state physics, materials science and metallurgy. However, new energy challenges in the world require devices with higher energy efficiency and minimum environmental impact. The potential of 3d-4f compounds that revolutionized PM science and technology is nearly fully utilized, and the supply of 4f rare earth elements is no longer assured.
This lecture will cover the major principles guiding the development of PMs, including the important role of microstructure on coercivity, and overview state-of-the-art theoretical and experimental research. Recent progress in the development of nanocomposite PMs, consisting of a fine (at the scale of magnetic exchange length) mixture of phases with high magnetization and large magnetic hardness will be discussed. Fabrication of such PMs is currently the most promising way to boost the (BH)max, while simultaneously decreasing, at least partially, the reliance on the rare earth elements. Current efforts in the development of high performance non-rare earth magnets and their future prospects will also be discussed.
Shinji YuasaNational Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
A magnetic tunnel junction (MTJ) consisting of a thin insulating layer (a tunnel barrier) sandwiched between two ferromagnetic electrodes exhibits the tunnel magnetoresistance (TMR) effect due to spin-dependent electron tunneling. Since the discovery of room-temperature TMR in the mid-1990s, MTJs with an amorphous aluminum oxide (Al–O) tunnel barrier have been studied extensively. Such MTJs exhibit a magnetoresistance (MR) ratio of several tens of percent at room temperature (RT) and have been applied to magnetoresistive random access memory (MRAM) and the read heads of hard disk drives. MTJs with MR ratios substantially higher than 100%, however, are desired for next-generation spintronic devices. In 2001, first-principle theories predicted that the MR ratios of epitaxial Fe/MgO/Fe MTJs with a crystalline MgO(001) barrier would be over 1000% due to the coherent tunneling of specific Bloch states. In 2004, MR ratios of about 200% were obtained for MgO-based MTJs . MTJs with a CoFeB/MgO/CoFeB structure were developed for practical application and found to have MR ratios of above 200% and other practical properties [1,2].This lecture focuses on the physics of magnetoresistance and spin-transfer torque in MTJs and the application of MTJs to various spintronic devices such as magnetic sensors, spin-transfer-torque MRAM (STT-RAM or spin-RAM) with perpendicular magnetization, and novel spin-torque oscillators. In addition, new types of MTJs such as spin-filter junctions with a ferromagnetic tunnel barrier will be discussed.
 S. Yuasa and D. D. Djayaprawira, J. Phys. D: Appl. Phys. 40, R337 (2007). D. D. Djayaprawira, K. Tsunekawa, M. Nagai, H. Maehara, S. Yamagata, N. Watanabe, S. Yuasa, Y. Suzuki and K. Ando, Appl. Phys. Lett. 86, 092502 (2005).
Gerrit E.W. BauerInstitute of Materials Research, Tohoku University, Japan, and Kavli Institute of NanoScience, TU Delft, The Netherlands.
The spin degree of freedom of the electron affects not only charge, but also heat and thermoelectric transport, leading to new effects in small structures that are studied in the field of spin caloritronics (from calor, the Latin word for heat).
This lecture addresses the basic physics of spin caloritronics. Starting with an introduction into thermoelectrics and Onsager’s reciprocity relations, the generalization to include the spin dependence in the presence of metallic ferromagnets will be addressed. Using this foundation I will describe several recently discovered spin-dependent effects in metallic nanostructures and tunneling junctions as well as a zoo of spin-related thermal Hall effects in terms of a two spin-current model of non-interacting electrons (an overview of the recent literature is given in Ref. 1).
Next, I will argue that different classes of spin caloritronic effects exists that can be explained only by the collective spin dynamics in ferromagnets. The thermal spin transfer torque that allows excitation and switching of the magnetization in spin valves as well as the operation of nanoscale heat engines is complemented by thermal spin pumping. The latter generates the so-called spin Seebeck effect, which is generated by a heat current-induced non-equilibrium of magnons at a contact between an insulating or conducting ferromagnet and a normal metal. Under these conditions a net spin current is injected or extracted from the normal metal that can be detected by the inverse spin Hall effect.
Both classes can be formulated by scattering theory of transport in the adiabatic approximation for the magnetization dynamics and computed in terms of material-dependent electronic structures. Further issues to be addressed are the relation between electric, thermal and acoustic actuation, as well as the application potential of spin caloritronics.
 G.E.W. Bauer, in Spin Currents, edited by S. Maekawa, E. Saitoh, S. Valenzuela and Y. Kimura (Oxford University Press, in press), arXiv:1107.4395.
Masahiro YamaguchiDepartment of Electrical and Communication Engineering, Tohoku University
Development of new passive component technologies will enable a “More-than-Moore” paradigm leading to innovative application-specific compact systems . Ferromagnetic thin film materials, having high permeability at (and above) radio frequencies, are candidate materials for use in inductive passive components that are available in the forms of vacuum-deposited and electro-deposited metallic alloys, chemically synthesized nano-particulate composites, and traditional oxides, among others. Using these materials, the development of CMOS integrated inductors and integrated electromagnetic noise suppressors for Long Term Evolution, or 3.9th Generation, cell phone RFIC and Point-of-Load one-chip DC-DC converters, is attracting great interest from both academic and industrial communities.
This lecture begins with a review of new soft magnetic thin film applications at radio frequencies for future system-in-package (SiP) and system-on-chip (SoC) technologies. Proposed in late 1970s, these thin film soft magnet applications have evolved from inductive read/write recording head technology to the frontiers of GHz frequency device applications. Discussions covered in this lecture include: (1) Development of international cross measurements of RF permeameters  to evaluate RF permeability and related FMR profiles of magnetic films; (2) small signal high permeable low loss applications to CMOS integrated inductors ; (3) small signal lossy application to CMOS integrated electromagnetic noise suppressor ; (4) small to medium signal applications as new metal/ferromagnetic multi-stack “conductors” to suppress skin effect utilizing negative permeability beyond the FMR frequency [μr’< 0, μr”≈0]; and, (5) large current permeable application to Point-of-Load type one-chip DC-DC converters. The lecture will conclude with an outlook that provides a perspective on the future of on-chip RF magnetics.
John P. Kent, and Jagdish Prasad, “Microelectronics for the Real World: ‘Moore’ versus ‘More than Moore’,” IEEE 2008 Custom Integrated Circuits Conference, 15-4-1 (2008).
M. Yamaguchi, Y. Miyazawa, K. Kaminishi and K.I. Arai, “A New 1 MHz-9 GHz Thin-Film Permeameter Using a Side-Open TEM Cell and a Planar Shielded-Loop Coil,” Trans. Magnetic Society of Japan, 3, 137-140 (2003).
Masahiro Yamaguchi, Keiju Yamada, Ki Hyeon Kim, "Slit Design Consideration on the Ferromagnetic RF Integrated Inductor," IEEE Transactions on Magnetics, 42, 3341-3343 (2006)
Sho Muroga, Yasushi Endo, Wataru Kodate, Yoshiaki Sasaki, Kumpei Yoshikawa, Yuta Sasaki, Makoto Nagata Masahiro Yamaguchi, “Evaluation of Thin Film Noise Suppressor Applied to Noise Emulator Chip Implemented in 65nm CMOS technology,” IEEE Transaction on Magnetics, 48, 4485 - 4488 (2011).
Masahiro Yamaguchi, Yutaka Shimada, Takayoshi Inagaki and Behzad Rejaei, “Skin Effect Suppression in RF Devices Using a Multilayer of Conductor and Ferromagnetic Thin Film with Negative Permeability,” Microwave Workshop and Exhibition 2008 (MWE 2008), WS08-03 (Yokohama, 2008).