Several skyrmion systems (stable magnetic perturbations of whirling spins [magnetic moments]) have been discovered, yet it remains a challenge for researchers to produce controllable, nanometer-sized skyrmions for technology needs.
In a new study, a team from the Institute for Basic Science discovered that skyrmions with a diameter smaller than 100 nm spontaneously form in ultrathin material, consisting of a layer of barium titanate (BaTiO3) and a layer of strontium ruthenate (SrRuO3). Below 160 Kelvin (–113 Celsius), SrRuO3 is ferromagnetic, meaning that its spins are aligned uniformly in a parallel fashion. When the two layers are overlaid, however, a special magnetic interaction swirls SrRuO3’s spins, generating magnetic skyrmions. This magnetic structure was detected below 80 Kelvin (–193 Celsius) by using magnetic force microscopy and Hall measurements.
In addition, by manipulating the ferroelectric polarization of the BaTiO3 layer, the scientists were able to change the skyrmions’ density and thermodynamic stability. The modulation is nonvolatile (i.e., it persists when the power is turned off), reversible, and nanoscale.
“Magnetic skyrmions and ferroelectricity are two important research topics in condensed matter physics. They are usually studied separately, but we brought them together,” said first study author Lingfei Wang. “This correlation provides an ideal opportunity to integrate the high tunability of well-established ferroelectric devices with the superior advantages of skyrmions into next-generation memory and logic devices.”