Spin-degree manipulation for one-dimensional room-temperature ferromagnetism in a haldane system

Exotic ferromagnetic order up to ∼700 K has been introduced in the well-known S = 1 Haldane system nickelate, Y 2 BaNiO 5 , induced by locally mixed S = 1 and 1/2 states (d 8 -Ni 2+ and d 9 -Ni + ) and oxygen vacancies along the finite chain segments.