Multiple Metamagnetic Quantum Criticality in Sr_{3}Ru_{2}O_{7}.

Area of Science:

• Condensed matter physics
• Quantum materials science
• Magnetism and magnetic materials

Background:

• Bilayer strontium ruthenate (Sr_{3}Ru_{2}O_{7}) exhibits non-Fermi liquid behavior near 8 T.
• This behavior has been linked to an itinerant metamagnetic quantum critical end point (QCEP).

Purpose of the Study:

• To directly probe field-induced quantum criticality in Sr_{3}Ru_{2}O_{7} using the magnetic Grüneisen parameter (Γ_{H}).
• To confirm and characterize the QCEP associated with non-Fermi liquid behavior.
• To investigate the influence of ordered phases on quantum criticality.

Main Methods:

• Measurement of the magnetic Grüneisen parameter (Γ_{H}) as a function of magnetic field.
• Analysis of quantum critical scaling.
• Consideration of neutron scattering data for ordered phases A and B.

Main Results:

• Confirmation of quantum critical scaling associated with a two-dimensional QCEP near 7.845(5) T.
• Identification of a second QCEP at 7.53(2) T.
• Characterization of quantum critical regimes and the superposition of instabilities.

Conclusions:

• The study provides direct evidence for field-induced quantum criticality in Sr_{3}Ru_{2}O_{7}.
• The interplay between QCEPs and ordered phases is crucial for understanding the material's complex magnetic properties.
• This work advances the understanding of quantum critical phenomena in correlated electron systems.