Observation of two-dimensional spin fluctuations in the bilayer ruthenateSr3Ru2O

Abstract

We report the first observation of two-dimensional incommensurate magnetic fluctuations in the layered metallic perovskite Sr3Ru2O7. The wavevectors where the magnetic fluctuations are strongest are different from those observed in the superconducting single layer ruthenate Sr2RuO4 and appear to be determined by Fermi surface nesting. No antiferromagnetic ordering is observed for temperatures down to 1.5 K. For temperatures T > ∼ 20 K, the fluctuations become predominately ferromagnetic. Our inelastic neutron scattering measurements provide concrete evidence of the coexistence of competing interactions in Sr3Ru2O7 and of the low energy scale of the fluctuations.78.70. Nx, 75.40.Gb, 74.20.Mn, 75.30.Kz

Magnetic excitations in the metallic single-layer ruthenates Ca2−xSrxRuOSteffens1, Friedt2, Sidis3 et al. 2011Phys. Rev. B

“…The structural and other variations in this range of x do not very sensitively couple to this part of the magnetic correlations. The rotational structural distortion, however, is apparently very important and causes a significant difference in Sr 2 RuO 4 24,26 In view of the similar Sr 3 Ru 2 O 7 crystal structure, which also exhibits the rotational distortion, 49 this appears consistent. These two layered ruthenates and their metamagnetic transitions appear to be very similar to each other.…”

“…17,18,[20][21][22][23] Furthermore, the bilayer compound Sr 3 Ru 2 O 7 has been investigated. [24][25][26] The excitations in these materials have the character of fluctuations that are both relatively broad in Q and ω. In Sr 2 RuO 4 , these fluctuations reside at Q = (0.3,0.3,0), i.e., at incommensurate wave vectors on the diagonal of the Brillouin zone.…”

Effect of magnetic field on spontaneous Fermi-surface symmetry breaking

“…Although a spontaneous dFSD has not been proposed for cuprates because of the competition with the d-wave singlet pairing, [1,3] [19] However, the material is close to a ferromagnetic transition, which was suggested by the strongly enhanced uniform magnetic susceptibility with a large Wilson ratio, [20] uniaxial-pressure-induced ferromagnetic transition, [21] inelastic neutron scattering, [22] and band structure calculations. [23,24] By applying a magnetic field h, Sr 3 Ru 2 O 7 shows a metamagnetic transition at h = h c , around which non-Fermi liquid behavior was observed in various quantities: resistivity, [25,26] specific heat, [26,27,28] thermal expansion, [29] and nuclear spin-lattice relaxation rate.…”

Hydrostatic pressure effects on the magnetic susceptibility of ruthenium oxide Sr3Ru2O7: evidence for pressure-enhanced antiferromagnetic instability

“…On the one side, a tendency to ferromagnetism is apparent, as exhibited by a strongly enhanced paramagnetic susceptibility with anomalously large [18][19][20] Wilson ratio (which is the dimensionless ratio of the low-temperature spin susceptibility to the electronic specific heat coefficient) R W > 10, and also by strong 2-D ferromagnetic spin correlations seen in neutron experiments. 21 On the other side, a strong antiferromagnetic instability is also present as evidenced [17][18][19] by the negative Weiss temperature, and a pronounced cusp in the temperature dependence of magnetic susceptibility at around T max = 16 K. The latter anomaly is also accompanied by anomalies in specific heat 18,19 , resistivity 17,19,22 , spectroscopy, confirming the ratio of Sr:Ru to be 3:2.…”

“…This, and also a theoretical prediction 14 and experimental observation 15 of antiferromagnetic spin fluctuations in Sr 2 RuO 4 (apparently driven by the Fermi-surface nesting), suggest that a tendency to antiferromagnetism might be a feature common to all ruthenates with a perovskite-derived structure, just as in cuprates. [17][18][19][20][21][22][23][24][25][26] . On the one side, a tendency to ferromagnetism is apparent, as exhibited by a strongly enhanced paramagnetic susceptibility with anomalously large [18][19][20] Wilson ratio (which is the dimensionless ratio of the low-temperature spin susceptibility to the electronic specific heat coefficient) R W > 10, and also by strong 2-D ferromagnetic spin correlations seen in neutron experiments.…”