The theories proposed by Albert Einstein and Wander Johannes de Haas discovered that when they used a magnetic field to flip the magnetic state of an iron bar dangling from a thread, the bar began to rotate.
A recent study at the Department of Energy’s SLAC National Accelerator Laboratory revealed how the magnetization would affect the particles magnetic field with an ultrafast speed of millionths of a billionth of a second. The atoms on the surface of the material move, much like the iron bar did. The work, done at SLAC’s Linac Coherent Light Source (LCLS) X-ray laser, was published in Nature earlier this month.
According to Christian Dornes, a scientist at ETH Zurich in Switzerland and one of the lead authors of the report, “this experiment shows how ultrafast demagnetization goes hand in hand with what’s known as the Einstein-de Haas effect,has solved a long term mystery in the field of magnetization.”
The transfer of angular momentum actually makes something move mechanically is really cool,” Dornes says. “Being able to work on the atomic scale like this and see relatively directly what happens would have been a total dream for the great physicists of a hundred years ago.”he denoted the works Einsteen and de Haas had done before.
The spin rotation in the atoms create a magnetic force,whereas in strong magnets, the magnetism comes from a quantum property of electrons called spin. Although electron spin does not involve a literal rotation of the electron, the electron acts in some ways like a tiny spinning ball of charge. On applying an external magnetic field this arranged spin rotation which creates the magnetic momentum which is in a unison would change and the spin motion become in every direction and the net result will become zero.
In their experiment, the researchers used a new technique at LCLS combined with measurements done at ETH Zurich to link these two phenomena. They demonstrated that when a laser pulse initiates ultrafast demagnetization in a thin iron film, the change in angular momentum is quickly converted into an initial kick that leads to mechanical rotation of the atoms on the surface of the sample.The researchers blasted the iron film with laser pulses to initiate ultrafast demagnetization, then grazed it with intense X-rays at an angle so shallow that it was nearly parallel to the surface. They used the patterns formed when the X-rays scattered off the film to learn more about where angular momentum goes during this process.