QCD phase diagram with a background magnetic field in an improved soft-wall AdS/QCD model Zhen Fang, Ying-Ying Li and Yue-Liang Wu Eur. Phys. J. C, 81 6 (2021) 545 Published online: 25 June 2021 DOI: 10.1140/epjc/s10052-021-09311-5