Spin–orbit coupled molecular quantum magnetism realized in inorganic solid

Molecular quantum magnetism involving an isolated spin state is of particular interest due to the characteristic quantum phenomena underlying spin qubits or molecular spintronics for quantum information devices, as demonstrated in magnetic metal–organic molecular systems, the so-called molecular magnets. Here we report the molecular quantum magnetism realized in an inorganic solid Ba 3 Yb 2 Zn 5 O 11 with spin–orbit coupled pseudospin-½ Yb 3+ ions. The magnetization represents the magnetic quantum values of an isolated Yb 4 tetrahedron with a total (pseudo)spin 0, 1 and 2. Inelastic neutron scattering results reveal that a large Dzyaloshinsky–Moriya interaction originating from strong spin–orbit coupling of Yb 4 f is a key ingredient to explain magnetic excitations of the molecular magnet states. The Dzyaloshinsky–Moriya interaction allows a non-adiabatic quantum transition between avoided crossing energy levels, and also results in unexpected magnetic behaviours in conventional molecular magnets. Molecular magnets may provide fundamental building blocks for future spintronic and quantum information technologies. Here, the authors demonstrate how the Yb 4 tetrahedral components of inorganic materials Ba 3 Yb 2 Zn 5 O 11 behave as isolated molecular magnets.