Magnetic order at the border: NMR and NQR as a microscopic tool

Abstract: Strongly correlated electron systems exhibit unconventional magnetic and electronic properties due to the presence of competing interactions. As a consequence of this competition combined with quantum ?uctuations, the critical temperatures of phase transitions may continuously approach zero and a quantum critical point (QCP) emerges. Ferromagnetic quantum criticality (FMQC) have been less explored so far than antiferromagnetic quantum criticality. In several systems lots of attempts by chemical and mechanical pressure have been made to get FMQC point but most of the cases the second order phase transition becomes first order or the system enters into a disordered phase (Griffiths phase, glassy state etc.) before reaching to the critical point which implies avoided FMQC. Interestingly in some disorder free systems due to QC fluctuations the systems enters into novel states (e.g. superconductivity, spiral state etc.) as well. We have employed NMR and NQR as a local tool to study the quantum critical spin-fluctuations in two putative ferromagnetic quantum critical systems namely Ge doped FeGa3 and V doped CeTiGe3. I will present the results obtained from NMR and NQR in those two systems and discuss about the possibility for the evidence of FMQCP in those two mentioned systems.