Multiferroic MnTiO3 (MTO) is made up of alternate Mn2+ (3d(5)) and Ti4+ (3d(0)) layers along the c-axis. It undergoes a magnetic spin-flop driven ferroelectric polarization flop beyond similar to 6 T below T-N similar to 64 K. MTO also exhibits a weak negative thermal expansion along the c-axis below similar to 90 K. We demonstrate that doping Mn ions at non-magnetic Ti layers acts as a very effective microscopic control parameter to systematically tune both these functional responses. Tuning of c/a lattice parameters in MnTi1-xMnxO3 leads to significant reduction in the spin-flop critical magnetic field from similar to 6 T to more easily accessible fields (< 2 T for x = 0.05). Simultaneously, the controlled tuning of magnetic frustration due to Mn-doping at Ti sites also helps in a systematic enhancement of anomalous thermal expansion in regard to increasing the onset temperature for anomalous expansion to higher values (by similar to 40 K for x = 0.10) and also strengthening its magnitude (by similar to 30% at 15 K for x = 0.10 in comparison to x = 0.00). Increase in the c/a ratio with Mn doping in MnTiO3 likely causes reduction in the effective magnetocrys-talline anisotropy, which leads to a decrease in the value of the spin-flop magnetic field. Detailed temperature-dependent structural analyses shed light on the critical role of exchange striction mechanism in tuning the negative thermal expansion in doped MnTiO3. Published under an exclusive license by AIP Publishing.
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