Anisotropic heat transport via monopoles in the spin-ice compound Dy2Ti2O7

Abstract

We report a study of the thermal conductivity κ of the spin-ice material Dy2Ti2O7. From the anisotropic magnetic-field dependence of κ and by additional measurements on the phononic reference compounds Y2Ti2O7 and (Dy0.5Y0.5)2Ti2O7, we are able to separate the phononic and the magnetic contributions to the total heat transport, i.e. κ ph and κmag, respectively, which both depend on the magnetic field. The field dependent κ ph (B) arises from lattice distortions due to magnetic-field induced torques on the non-collinear magnetic moments of the Dy ions. For κmag, we observe a highly anisotropic magnetic-field dependence, which correlates with the corresponding magnetization data reflecting the different magnetic-field induced spin-ice ground states. The magnitude of κmag increases with the degree of the ground-state degeneracy. This anisotropic field dependence as well as various hysteresis effects suggest that κmag is essentially determined by the mobility of the magnetic monopole excitations in spin ice.

Hysteresis and Relaxation Effects in the Spin-Ice Compound Dy2Ti2O7 Studied by Heat Transport

“…[20] in measurements with the heat current  along and perpendicular to the magnetic field, i.e. with  perpendicular and within the kagome planes, respectively, and has been confirmed by our data [17] measured with  || [110]. However, according to Ref.…”

“…At low temperature, the kagome-ice phase is characterized by a plateau in the magnetization M(H) up to about 1 T, where a transition to the fully polarized state occurs. Surprisingly, κ(H) is strongly hysteretic within the kagome-ice phase [17,20], whereas there is no hysteresis in the corresponding magnetization plateau. This unusual hysteresis of κ(H) has been observed in Ref.…”

Possible observation of highly itinerant quantum magnetic monopoles in the frustrated pyrochlore Yb2Ti2O7

“…The thermal conductivity has been reported in the classical spin-ice state of Dy 2 Ti 2 O 7 recently1920. However, the interpretation of the thermal conductivity of Dy 2 Ti 2 O 7 appears to be complicated owing to the strongly suppressed phonon thermal conductivity by unknown additional scatterings (Supplementary Fig.…”

Suppression of Pauling's residual entropy in the dilute spin ice(Dy1−xYx)2Ti2Scharffe1, Breunig2, Cho3 et al. 2015Phys. Rev. BSelf Cite

“…As a consequence of the ground-state degeneracy, each pair fractionalizes into two individual excitations that can be described as magnetic (anti-)monopoles propagating independently through the lattice [3,4,11,12]. The dynamics of these monopole excitations is subject of intense research [5,[13][14][15][16].Experimental evidence for Pauling's residual entropy in spin-ice systems stems from specific heat measurements [17][18][19][20] reporting a practically temperatureindependent entropy S ex (T ≈ 0.4 K) ≃ S P . More recently, however, extremely slow relaxation phenomena were observed for Dy 2 Ti 2 O 7 in low-temperature measurements of, e.g., the magnetization [21,22], ac susceptibility [23], thermal transport [24,25] or the specific heat [24,26,27].…”

“…As a consequence of the ground-state degeneracy, each pair fractionalizes into two individual excitations that can be described as magnetic (anti-)monopoles propagating independently through the lattice [3,4,11,12]. The dynamics of these monopole excitations is subject of intense research [5,[13][14][15][16].…”