Evolution of Magnetism Induced by K⁺/La³⁺ Implantations in Double Perovskite Ba₂MnTeO₆

B -site rock salt type ordered double perovskites with general formula A 2 B′B ″ X 6 have attracted a variety of attention due to remarkable magnetic properties and potential applications in spintronics. Here we report the structural, magnetic, and electronic properties of polycrystalline compounds Ba 2 MnTeO 6 and (Ba 0.9 X 0.1 ) 2 MnTeO 6 (X = K/La) by powder X-ray diffraction, magnetic susceptibility measurements, specific heat measurements, and X-ray photoelectron spectroscopy. Ba 2 MnTeO 6 is antiferromagnetically ordered below 20 K. Density functional theory calculations show that Ba 2 MnTeO 6 prefers type III antiferromagnetic order with a dominant antiferromagnetic nearest-neighbor exchange and a weak ferromagnetic next-nearest-neighbor exchange. Our Monte Carlo simulations lead to a transition temperature of 28 K, consistent with the experimental results. Upon K + /La 3+ cations’ implantation on Ba sites, while (Ba 0.9 K 0.1 ) 2 MnTeO 6 orders antiferromagnetically at 20 K, (Ba 0.9 La 0.1 ) 2 MnTeO 6 exhibits superparamagnetism below room temperature, which may originate from oxygen ion adsorptions. These findings reveal the modulation of magnetism for Ba 2 MnTeO 6, which may hint at potential applications of double perovskites in magnetic devices.