Using magnetism to cool your chips

A new technology in the magnetic cooling of chips based on the straining of materials is claimed will lessen the impact on the environment compared to current technologies.

Current cooling systems, be they refrigerators, freezers or air-conditioning units, make use of the compression and expansion of a gas. When the gas is compressed, it changes into a liquid state; and when it expands, it evaporates once again. To evaporate, it needs heat, which it extracts from the medium it touches and that way cools it down. However, this system is harmful for the environment and, what is more, the compressors used are not particularly effective.

One of the main alternatives that is currently being explored is magnetic cooling. It consists of using a magnetic material instead of a gas, and magnetising and demagnetising cycles instead of compression-expansion cycles. Magnetic cooling is a technique based on the magnetocaloric effect; in other words, it is based on the properties displayed by certain materials to modify their temperature when a magnetic field is applied to them. However, the applying of a magnetic field leads to many problems in current miniaturised technological devices (electronic chips, computer memories, etc), since the magnetic field can interact negatively owing to its effect on nearby units. In this respect, the quest for new ways of controlling the magnetisation is crucial.

CIC nanoGUNE researchers Luis Hueso, Andreas Berger and Odrej Hovorka have discovered that by using the straining of materials, they can get around the problems of applying a magnetic field. “By straining the material and then relaxing it, an effect similar to that of a magnetic field is created, thus inducing the magnetocaloric effect responsible for cooling,” explains Luis Hueso, leader of the nanodevices group at nanoGUNE and researcher in this study.

“This new technology enables us to have a more local and more controlled cooling method, without interfering with the other units in the device, and in line with the trend in the miniaturisation of technological devices,” adds Hueso.

20 nm films consisting of lanthanum, calcium, manganese and oxygen (La_0.7Ca_0.3MnO₃) have been developed. According to Hueso, “The aim of this field of research is to find materials that are efficient, economical and environmentally friendly.”

“The idea came about at Cambridge University, and among various groups in the United Kingdom, France, Ukraine and the Basque Country, we have come up with the right material and an effective technique for cooling electronic chips, computer memories and all these types of applications in microelectronics. Technologically, there would not be any obstacle to using them in fridges, freezers etc, but economically it is not worthwhile because of the size,” stresses Hueso.

Today, most of the money spent on the huge data servers goes on cooling. That is why this new technology could be effective in applications of this kind. Likewise, one of the great limitations that computer processors have today is that they cannot operate as fast as one would like because they can easily overheat. “If we could cool them down properly, they would be more effective and could work faster,” adds Hueso.

The work has been published recently in the journal Nature Materials.