A "supercooled" liquid develops when a fluid does not crystallize upon cooling below its ordering temperature. Instead, the microscopic relaxation times diverge so rapidly that, upon further cooling, equilibration eventually becomes impossible and glass formation occurs. Classic supercooled liquids exhibit specific identifiers including microscopic relaxation times diverging on a Vogel-TammannFulcher (VTF) trajectory, a Havriliak-Negami (HN) form for the dielectric function e(ω, T ), and a general Kohlrausch-Williams-Watts (KWW) form for time-domain relaxation. Recently, the pyrochlore Dy 2 Ti 2 O 7 has become of interest because its frustrated magnetic interactions may, in theory, lead to highly exotic magnetic fluids. However, its true magnetic state at low temperatures has proven very difficult to identify unambiguously. Here, we introduce highprecision, boundary-free magnetization transport techniques based upon toroidal geometries and gain an improved understanding of the time-and frequency-dependent magnetization dynamics of Dy 2 Ti 2 O 7 . We demonstrate a virtually universal HN form for the magnetic susceptibility χ (ω, T ), a general KWW form for the realtime magnetic relaxation, and a divergence of the microscopic magnetic relaxation rates with the VTF trajectory. Low-temperature Dy 2 Ti 2 O 7 therefore exhibits the characteristics of a supercooled magnetic liquid. One implication is that this translationally invariant lattice of strongly correlated spins may be evolving toward an unprecedented magnetic glass state, perhaps due to many-body localization of spin.spin liquid | supercooled liquids | magnetic dynamics | periodic boundaries C ooling a pure liquid usually results in crystallization via a first-order phase transition. However, in glass-forming liquids when the cooling is sufficiently rapid, a metastable "supercooled" state is achieved instead (1-3). Here, the microscopic relaxation times diverge until equilibration of the system is no longer possible at a given cooling rate. At this juncture there is generally a broad peak in the specific heat preceding the glass transition, at which no symmetry-breaking phase transition occurs (Fig. 1A). The antecedent fluid exhibits a set of phenomena characteristic of the supercooled liquid state (1-3). For example, the divergence of microscopic relaxation times τ 0 ðTÞ typically shows substantial departures from Arrhenius behavior [τ 0 ðTÞ = AexpðΔ=kTÞ and, instead, is described characteristically using the Vogel-Tammann-Fulcher (VTF) form (4)Here, T 0 is a temperature at which the relaxation time diverges to ∞ while D characterizes the extent of the super-Arrhenius behavior (Fig. 1B). One way to establish τ 0 ðTÞ is by measuring the characteristic frequency ω 0 ðTÞ = 1=τ 0 ðTÞ of peaks in the dissipative (imaginary) component of the dielectric function «ðω, TÞ.For classic supercooled liquids, «ðω, TÞ generally exhibits the Havriliak-Negami (HN) form (5, 6) «ðω,[2]Here, the exponents α and γ describe, respectively, the broadening and asymmetry of the rela...

The Cornell University energy recovery linac (ERL) photoinjector has recently demonstrated operation at 20 mA for approximately 8 hours, utilizing a multialkali photocathode deposited on a Si substrate. We describe the recipe for photocathode deposition, and will detail the parameters of the run. Post-run analysis of the photocathode indicates the presence of significant damage to the substrate, perhaps due to ion back-bombardment from the residual beam line gas. While the exact cause of the substrate damage remains unknown, we describe multiple surface characterization techniques (x-ray fluorescence spectroscopy, x-ray diffraction, atomic force, and scanning electron microscopy) used to study the interesting morphological and crystallographic features of the photocathode surface after its use for high current beam production. Finally, we present a simple model of crystal damage due to ion back-bombardment, which agrees qualitatively with the distribution of damage on the substrate surface.

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