High-pressure crystal growth and investigation of the metal-to-metal transition of Ruddlesden-Popper trilayer nickelates La4Ni3O10

Single crystals of Ruddlesden-Popper nickelates La4Ni3O10 were grown by means of the floating-zone technique at oxygen pressure of 20 bar. Our results reveal the effects of the annealing process under pressure on the crystal structure. We present the requirements for crystal growth and show how a reported ferromagnetic impurity phase can be avoided. The different growth and post-annealing processes result in two distinct phases P21/a and Bmab in which the metal-to-metal transitions occur at 152 K and 136 K, respectively.