A question on atoms

[aldiboronti]

Specifically holmium atoms.

In this Gizmodo article on single atom data storage I read the following.

Natterer’s work build on previous efforts to create single-atom magnets. He started with holmium, one of the stranger elements on the periodic table. Lots of the electrons orbiting holmium’s nucleus buzz around without a partner, unlike more familiar elements, he explained.

The researchers embedded these holmium atoms in a metal, in this case magnesium oxide, which prevents holmium’s magnetic field from falling apart under the influence of other electrons or vibrations.

I don’t understand this. If the goal is to prevent the magnetic field falling apart owing to the influence of other electrons or vibrations how does embedding the holmium atoms in a metal help? Aren’t metals themselves bunches of electrons and vibrations?

[naita]

Beyond my understanding, but the original article in nature is linked from the gizmondo piece: Stabilizing the magnetic moment of single holmium atoms by symmetry

[naita]

@naita

Beyond my understanding, but the original article in nature is linked from the gizmondo piece: Stabilizing the magnetic moment of single holmium atoms by symmetry

Core explanation from the summary:

The necessary decoupling from the thermal bath of
electrons, nuclear spins and lattice vibrations is achieved by a
remarkable combination of several symmetries intrinsic to the sys-
tem: time reversal symmetry, the internal symmetries of the total
angular momentum and the point symmetry of the local envir-
onment of the magnetic atom.

[aldiboronti]

Thanks, guys, but I’m minded of Byron’s verse on Coleridge

Explaining metaphysics to the nation,
I wish he would explain his explanation!

Maybe this is just something that can’t be put in layman’s terms but I’m still lost.

[am77494]

Imagine a bunch of colored pushpins lying in a bowl. You want to study how each push pin behaves as a magnet. So you take the pushpins and put them on a cork board.

The atoms are like the pushpins and the magnesium oxide is the cork board. Magnesium oxide is an insulator/ceramic and does not conduct - so one atom cannot influence the other one once embedded.

[tim314]

Basically, for the atom to function as a miniature magnet you want to keep it aligned in a given direction. But because the atom has the same energy no matter which way it’s turned, it’s way too easy to bump it out of alignment.

However, if you place the atom on a substrate, the electrostatic interactions between the original atom and the atoms in the substrate can mean it now has a different amount of energy depending on which way it’s turned. That makes it harder to bump it out of alignment, because you’d have to provide at least enough energy to make up the difference between its orientation before the bump and its orientation afterwards.

That part isn’t new. The problem though is this doesn’t give as much stability as you would hope, due to an effect of the electrons from the substrate atoms mixing with the electrons of the original atom. The new work is that these researches found that by imbedding the atom in a lattice of rare earth atoms with a certain crystal structure, they could produce states whose differing symmetry prevented them from mixing together, and thus further stabilize the “magnet” atom.

[aldiboronti]

@am77494

Imagine a bunch of colored pushpins lying in a bowl. You want to study how each push pin behaves as a magnet. So you take the pushpins and put them on a cork board.

The atoms are like the pushpins and the magnesium oxide is the cork board. Magnesium oxide is an insulator/ceramic and does not conduct - so one atom cannot influence the other one once embedded.

Thank you, am77494, that I can follow!

[tim314]

Or to boil it down a bit more from my previous response:

In quantum mechanics, certain transitions between states are allowed, and other transitions are forbidden, for reasons related to symmetry. These researchers have created a setup where some of the transitions that would destabilize the atom are forbidden, making it more stable.

In particular, they say that in certain states a single electron from the substrate knocking the atom from one low-energy state to another is forbidden, and instead you’d need to have something like one electron knocking the atom hard enough to send it into a higher energy state, followed by another knocking it down into the new low-energy state. That’s going to happen less often, so the atom stays in its state longer.