A novel synthetic material made from 1 billion tiny magnets in a honeycomb pattern undergoes phase transitions as the temperature changes, similar to the way water can switch between gaseous, liquid and solid states.Researchers at the Paul Scherrer Institute (PSI) in Switzerland have created a synthetic material made from 1 billion tiny magnets. Astonishingly, it now appears that the magnetic properties of this so-called metamaterial change with temperature, allowing it to take on different physical states, just like water can exist in gaseous, liquid and solid states. This material made of nanomagnets could well be refined for future electronic applications, such as more efficient information transfer.
The switching between physical states, known as a phase transition, was observed by a team of researchers headed by Laura Heyderman from PSI. "We were surprised and excited," explains Heyderman. "Only complex systems are able to display phase transitions." And as complex systems can provide new kinds of information transfer, this study suggests that the PSI researchers' metamaterial would be a potential candidate for this kind of application.
A major advantage of the synthetic metamaterial is that it can be easily customized. While the individual atoms in a natural material cannot be rearranged with pinpoint precision on such a grand scale, the researchers say this is possible with the nanomagnets, which are only 63nm long and shaped roughly like grains of rice. The researchers used a highly advanced technique to place 1 billion of these tiny grains on a flat substrate to form a large-scale honeycomb pattern that covered a total area of 5mmx5mm.
Thanks to a special measuring technique, the scientists were able to begin by studying the collective magnetic behavior of their metamaterial at room temperature. Under these conditions, there was no order in the magnetic orientation: the magnetic north and south poles pointed randomly in one direction or another.
When the researchers gradually and constantly cooled the metamaterial, however, they reached a point where a higher order appeared: the tiny magnets now interacted with each other more than before. As the temperature fell further, there was another change towards an even higher order, in which the magnetic arrangement appeared almost frozen. The long-range order of water molecules increases in a similar way as liquid water freezes into ice. "We were fascinated by the fact that our synthetic material displayed this everyday phenomenon of a phase transition," says Heyderman.
Next, the researchers are planning to investigate these magnetic phase transitions by altering the size, shape and arrangement of the nanomagnets. This could lead to the creation of new states of matter, potentially giving rise to novel applications: "The beauty of it all: tailored phase transitions could enable metamaterials to be adapted specifically for different needs in future," explains Heyderman.
Besides its potential use in information transfer, the metamaterial might also prove useful in data storage or for sensors that measure magnetic fields. It could also potentially be used in spintronics, where the spin of an electron is used for computer processing.
The measurements the researchers used to reveal the magnetic orientation of the nanomagnets, and therefore the properties of the metamaterial, could only be conducted at PSI. This is because PSI houses unique equipment able to produce beams from exotic elementary particles called muons, which can be used to study nanomagnetic properties. The project took place in collaboration with a research group headed by Stephen Lee from the University of St Andrews in Scotland, and is reported in a paper in Nature Communications.
This story is adapted from material from PSI, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.