The researchers grew a sheet of yttrium iron garnet using laser molecular beam epitaxy in a laboratory (abstract). Magnetic substances like iron are known to disrupt graphene's electrical conduction properties, but yttrium iron garnet works well as it is an electric insulator.
When a graphene sheet was placed on top of an atomically smooth sheet of yttrium iron garnet, the graphene borrowed the magnetic properties from the yttrium iron garnet and became magnetized without the need for doping.
Kone's creation was chosen to be installed in what's destined to become the world's tallest building, the Kingdom Tower in Jeddah, Saudi Arabia. When completed in 2020, the tower will stand a full kilometer in height, and will boast the world's tallest elevator at 660m (2,165ft). A 1km-tall tower may seem staggering, but is this the build-able limit? Most probably not, according to Dr. Sang Dae Kim. "With Kingdom Tower we now have a design that reaches around 1 km in height. Later on, someone will push for 1 mile, and then 2 km," says Kim. He adds that, technically speaking, 2 km might be possible at the current time. Anything higher would require new materials and building techniques.