Frustrated materials under high pressure

Frustrated materials under high pressure

Researchers modify magnetic behavior of exotic materials

People are not the only ones to be occasionally frustrated. Some crystals also show frustrations. They do so whenever their elementary magnets, the magnetic spins, cannot align properly. Cesium copper chloride (Cs2CuCl4) – or CCC for short – is a prime example of frustrated materials. In this crystal, the magnetic copper atoms reside on a triangular lattice and seek to align themselves antiparallel to each other. In a triangle, this does not work, however. This geometric frustration challenges physicists. After all, it promises the discovery of new magnetic phenomena that may even be used for quantum computers in the future. To better investigate and understand the underlying basics, physicists from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany, supported by Japanese and American colleagues, can now control the magnetic coupling using an elegant measuring method.

“Our aim is to elucidate the complex quantum processes in geometrically frustrated crystals in detail,” explains Dr. Sergei Zvyagin from the Dresden High Magnetic Field Laboratory at the HZDR. Theories about the magnetic behavior of crystals such as CCC abound. But so far, sophisticated experiments to test these theories on the object itself have been lacking. To this end, it is helpful to deliberately change the strength of the interactions between the magnetic atoms.

Physicists in many laboratories often take a tedious route: they produce crystals with geometric frustration in a slightly different chemical composition. This changes the magnetic interaction between the elementary magnets, but sometimes also – unintentionally – the crystal structure. Zvyagin left this laborious, purely chemical path to deeper knowledge. Instead, he used high pressures. Under these conditions, the strength of the coupling of the magnetic spins can be changed quasi-continuously.

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