Influence of La doping on the magnetic properties of the two-dimensional spin-gapped system SrCu$_2$(BO$_3$)$_2$Šibav, Lia (Avtor) Knaflič, Tilen (Avtor) King, Graham (Avtor) Jagličić, Zvonko (Avtor) Koblar, Maja (Avtor) Povarov, Kirill (Avtor) Zvyagin, Sergei (Avtor) Arčon, Denis (Avtor) Dragomir, Mirela (Avtor) antiferromagnetsdopingcrystal structureelectron paramagnetic resonance spectroscopyquantum mechanicsthermodynamic propertiesDoping of the two-dimensional dimer antiferromagnet SrCu$_2$(BO$_3$)$_2$ has long been proposed as a potential route toward realizing resonating valence bond superconductivity in this system; however, experimental progress has remained limited. This study explores the effects of La doping on the ground state of SrCu$_2$(BO$_3$)$_2$ and reports the first flux growth of Sr$_{1−x}$La$_x$Cu$_2$(BO$_3$)$_2$ single crystals with nominal doping levels up to x = 0.15. Powder X-ray diffraction and energy-dispersive X-ray spectroscopy confirm the successful incorporation of La on the Sr sites within the same tetragonal I$\overline 4$2m structure, although the effective doping was found to be <50% of the nominal concentration. La doping induces systematic changes in the magnetic properties of SrCu$_2$(BO$_3$)$_2$, with a reduction of the effective spin gap from 28.2 K for the undoped sample to 20.3 K for x = 0.15, as determined from the low-temperature magnetic susceptibility. The X-band electron spin resonance measurements reveal the emergence of unpaired Cu$^{2+}$ spins, which develop antiferromagnetic correlations below ∼5.5 K. These findings corroborate the breaking of the local spin dimers in SrCu$_2$(BO$_3$)$_2$ induced by La doping. No superconductivity is observed across the entire doping range studied.20262026-01-13 10:00:46Članek v reviji177911sl