Research Group

Interview with the staff of Mizuguchi Lab (Nano-Spin and Magnetic Materials Development Engineering Group)

Convert waste heat into electricity!
Our goal is to be! Energy-saving master who can freely control energy conversion!

(From left) Prof. Mizuguchi and Associate Prof. Miyamachi standing in front of the laboratory's experimental equipment.
Equipment for preparing a sample
Preparing samples that exhibit a variety of functions is very important in obtaining accurate and good data.

Do you know how much heat we humans release into the earth when we produce energy such as power and electricity? It is said that only about 40% of the original energy is utilized and 60% is thrown away into the atmosphere as heat. It is true that high heat is emitted in the engine room of a car when you run it, the outdoor unit of an air conditioner emits hot air when you run an air conditioner, and factories emit heat on a large scale.
At Mizuguchi Laboratory, they are mainly working on converting this waste heat, which accelerates global warming, into electrical energy. You may be wondering, "How is that possible? In fact, it's scientists and researchers who are trying to make a wish into a reality with the power of science!
This issue deals with the interview we had with two members of Mizuguchi Laboratory, who are trying to contribute to energy saving by freely manipulating energy conversion. It focuses on their research and its attractive points.

Convert waste heat into electricity!?

Masaki Mizuguchi


1998 Graduated from the University of Tokyo, 2003 Completed the doctoral program at the University of Tokyo, 2003 Special Research Fellow at the Japan Society for the Promotion of Science, 2004 Special Assistant at Osaka University, 2007 Assistant Professor at Tohoku University, 2009 Associate Professor at the same university, 2020 Professor at Nagoya University.
● His pastime and hobbies: Skiing, golf, scuba diving, dancing, reading, traveling, mahjong, karaoke, talking on the telephone, and many others. He likes to ride bikes, climb mountains, and watch and play baseball. He plays almost all kinds of musical instruments: piano, trumpet, guitar, and so on. But what he loves the most is drinking. Drinking with his wife on weekends is very special.

First of all, could you tell us about the characteristics of Mizuguchi Laboratory?

Mizuguchi:Energy has been the focus of a lot of attention in society and academia, and there are many different energy sources: not only water, wind, sunlight, but also sound, vibrations and electromagnetic waves can be used to generate electricity. We mainly use magnetic materials as a base to convert heat sources into electricity.

By heat source, do you mean something like the heat emitted from a car?

Mizuguchi:That's just one example. The engine and muffler of a car are very hot because of waste heat, but in the same way heat is thrown away as waste heat in many other places. Roughly, only 40% of the energy produced in the world is used and 60% is thrown away. We are working on the creation of materials and systems that can recover such discarded energy and convert other various energy sources, including heat, to generate new electrical power and make use of it.

You mean we can make electricity from waste heat!

Mizuguchi:To create energy, attention tends to be focused on completely new energy conversion technologies, but we are aiming to create materials with dramatically higher thermoelectric conversion efficiency by applying the thermomagnetic effect known as the "anomalous Nernst effect" (see upper right figure) to nanoscale*1 magnetic superstructures*2. We were perhaps the first to try to use this anomalous Nernst effect for converting energy from heat to electricity. Nowadays, it is a very competitive field in the world.

Conceptual diagram of the anomalous Nernst effect.
When a thermal gradient is applied to a magnetic material, a voltage is generated in the direction perpendicular to the thermal gradient and the magnetization.

Magnetic materials are the basis of our research.

What kind of materials do you use?

Mizuguchi:The base materials are so-called magnetic materials, such as iron, cobalt and nickel, which I think you all are all familiar with. By combining these simple elements with compounds, semiconductors, insulators and other magnetic materials, as well as metals, we can use the functions of magnetism and spin*3 to convert energy and create other phenomena that can be used in various fields of science.

Is it possible to make that happen in front of us?

Mizuguchi:Yes, we can. Thermoelectric conversion*4, or the conversion of heat to electricity, can be done by creating some kind of thermal gradient. For example, if we make something as large as a few centimeters in size out of the material I mentioned earlier, and soak one side in warm water to make one side hot and the other side cold, there will be a thermal gradient, right? If we do this, the light bulb connected to it will light up.

Only the difference in heat is needed to generates electricity!
The actual thermal gradient in the sample, as captured by the thermal camera. You can see that there is a temperature difference of about 2°C between the two places measured.

When did you start studying magnetic materials?

Mizuguchi:I have been working with magnetic materials since I was a student. I am very interested in magnetism. Magnets also stick to things, but they also attract researchers' feelings and interests. There are lots of different materials, and I have been working on this and that, but in the end, I have been focusing on research on magnets and spin. Magnetic materials are the basis of my research.

Observing the arrangement of atoms, one by one.

Associate Professor
Toshio Miyamachi


In 2005, he graduated from Osaka University. In 2008, he finished the doctoral course at the same university. In 2009, he became a doctor student at Karlsruher Institut für Technologie in Germany. In 2013, he was employed as Assistant Professor at the Institute for Solid State Physics, the University of Tokyo. In 2020, he became Assistant Professor (as an expert young researcher) on the tenure truck at the University of Electro-Communications. He has been an Associate Professor at Nagoya University since 2021.
● His pastime and hobby: overseas travel, joining beer drinking contests (awarded a master's degree in Germany), muscle training in a gym.

Associate Professor Miyamachi, what do you do in your research?

Miyamachi:I study magnetism and magnets, too, but what I mainly do is conduct researches on something far more microscopic. For example, I study the origin of magnetism of materials produced in Mizuguchi's laboratory at the level of a single atom. by observing them with the microscope.

You mean you can find out the origin of magnetism by atomic-level observation.

Miyamachi:I've conducted the basic research of clarifying fundamental questions such as why magnets attract (or repel) each other, and what magnets are themselves. For that purpose, I've observed the arrangements of atoms and the magnetic signals of a single atom. I am thinking now of working on the way to put the results to practical use in the real world.

How do you measure or evaluate?

Miyamachi:We use a scanning tunneling microscope*5 (STM), by which we can observe how the atoms on the surface of matter are arranged at level of atoms. We can find out how strong the matter is as magnet on atomic scale because it is possible to detect not only the concavo-convex information on the surface but also its magnetic signal. That's how we measure and evaluate.

I feel as if I were the tip of a probe! Do you understand?

What kind of difficulty do you have when you use the scanning tunneling microscope?

Miyamachi:Scanning tunneling microscopes, like electron microscopes, are subject to vibrations that cause the image to vibrate, so it is very important to suppress these vibrations. For example, if we are on the fifth floor of a building, the building vibrates three times in a second. We hardly sense it, but the vibrations are introduced as noise into the STM system. We also have to preserve the ultra high vacuum environment because it is also necessary to keep the surface of the material as clean as possible. It could be that the STM probe is not in good condition.

Does the tip of the probe have any effect on the results?

Mizuguchi:What we deal with at the last stage is a single atom. It probably depends on our experience whether we can control it by removing or placing it in a delicate way. I'm afraid we have to use our intuition when we cannot see it clearly. We have to guess where the tip of the probe is.

Miyamachi:I really feel like that. Now that I am accustomed to using the tip of the probe, I sometimes say to myself, "How do you feel now?" and even feel as if I were the needle myself. (hahaha)

The true joy of being scientists.

When do you feel very happy while conducting your research?

Mizuguchi:As you may imagine, I feel very happy when I discover something new. As every researcher says, scientists feel very happy when they realize they are the only persons who know it at the moment, though it may be just self-content. When they accomplish something. they also feel very happy to share the sense of accomplishment with the other staff of the lab. and the students working with them. They feel very happy, too, when they find their results have had social ramifications.

How about you, Professor Miyashita?

Miyamachi:Let me see. I feel very happy at a new discovery I make and at the appearance of my thesis in a magazine like Nature. I feel excited at the beauty of natural law when I have done so well that everything seems simple and straightforward. I think that is the true joy of science. It is extremely important indeed to draw a conclusion through complex calculations and analyses, but we feel excited at the moment we find a truth out of a simple phenomenon.

It is the true joy of being a researcher, isn't it? Will you please relate your experience?

Miyamachi:I'll tell you what I experienced about atomic magnetism. The origin is based on quantum mechanics and mathematics. I found out how a single atom can become a strong magnet when I opened a textbook of quantum mechanics. Later when I observed an atomic magnet by STM, I was able to verify that it was actually a stable and strong magnet in accordance with the law of quantum mechanics. I remember feeling impressed at that time and talking to myself, "Oh!"

A formula seemed to be composed of meaningless symbols, but when you saw with your own eyes what it meant, you realized you understood, didn't you?

Miyamachi:Yes, I did, and the formula is quite simple. I think one of the joys of science is to discover that the simple formula controls physical phenomena. What's more, our recent research shows that atomic-level physical phenomena if they are taken into account in the applied research one step forward from basic research, can lead to the realization of magnetic materials and devices with innovative properties. That's what keenly interests me now.

Some final words for young people who are going to be researchers, please.

Mizuguchi:In my opinion, young people should be young people. I don't refer to their appearance or their senses of value, but to their attitude to their own lives. I think there is something they cannot do unless they are young. They could confront life's challenges head-on. If they have passion for researches, I want them to conduct researches to their hearts' content. I think it is young researchers' privilege to be free from fixed ideas for research and to start thinking freely.

Basic Knowledge

*1 Nanoscale

The scale of the nanometer unit. In other words, a world with a size of 1/1 billionth of a meter. 1nm = 0.000000001

*2 Magnetic superstructures

A structure that creates new functions and properties by controlling the crystal and interface structures of magnetic materials and manipulating the spin inclination and spatial arrangement.

*3 Spin

A quantity related to the magnetism of a particle. It is a kind of motion that rotates on its own, and can be easily understood by using the image of "rotation," but it is different from the rotation of classical mechanics. When a magnetic force is applied from outside, the direction is the same (parallel) or opposite (antiparallel) to that of the magnetic force. By controlling the electron spin, it is possible to change the ease with which electric current flows, and this is attracting attention in the field of next-generation recording and circuit development.

*4 Thermoelectric Conversion

Thermoelectric conversion is a general term for phenomena that relate heat and electricity, such as the Seebeck effect, Pelletier effect, and Thomson effect. For example, when two different metals or semiconductors are bonded together and a temperature difference is generated at both ends, an electromotive force is generated, which is the Seebeck effect.

*5 Scanning Tunneling Microscope

Scanning Tunneling Microscope (STM) When the sharp point probe comes close to the surface of the sample with weak voltage between it and the conductive material, tunnel current runs. This current is sensitive to the change of the distance between the two, and if the tunnel current is kept at a constant strength while it is scanned, it is possible to trace the irregularity on the surface at atom-level scale. That is what has developed the study of surface science remarkably. Not only for the observation of semiconductors and metal surface, it is used in the wide field including organic materials and biomolecules. STM was invented by G. Binnig and H. Rohrer at IBM Research in Zurich in the beginning of the 1980's and the two of them were awarded the Nobel Prize in Physics in 1986 due to the achievement.

Text extracted from "IMaSS NEWS Vol. 11" Special Issue, IMaSS Publicity Committee (E. Ikenaga and M. Konishi)
[English translation by J. C. Oates]