Abstract
Strongly correlated electronic systems can harbor a rich variety of quantum spin states. Understanding and controlling such spin states in quantum materials is of great current interest. Focusing on the simple binary system UPt3 with ultrasound (US) as a probe we identify clear signatures in field sweeps demarkating new high field spin phases. Magnetostriction (MS) measurements performed up to 65 T also show signatures at the same fields confirming these phase transitions. At the very lowest temperatures (<200 mK) we also observe magneto-acoustic quantum oscillations which for θ = 90° (B||c-axis) and vicinity abruptly become very strong in the 24.8–30 T range. High resolution magnetization measurements for this same angle reveal a continuous variation of the magnetization implying the subtle nature of the implied transitions. With B rotated away from the c-axis, the US signatures occur at nearly the same field. These transitions merge with the separate sequence of the well known metamagnetic transition which commences at 20 T for θ = 0° but moves to higher fields as 1/cosθ. This merge, suggesting a tricritical behavior, occurs at θ ≈ 51° from the ab-plane. This is an unique off-symmetry angle where the length change along the c-axis is precisely zero due to the anisotropic nature of MS in UPt3 for all magnetic field values.
Highlights
Correlated electronic systems can harbor a rich variety of quantum spin states
This may appear as a step change, and may be termed a quantum phase transition (QPT)[1,2,3,4]
We present magnetostriction and high resolution magnetization measurements performed separately in further characterizing the state transitions implied by the US signatures
Summary
Correlated electronic systems can harbor a rich variety of quantum spin states. In such metamagnets a critical field Bc is observed for a specific orientation, but only a gradual increase being present when the field is in the perpendicular direction The latter is invariably the hard axis, exhibiting a smaller low-temperature susceptibility, in many cases by nearly an order of magnitude. UPt3 with a hexagonal crystal structure is one of the earliest discovered HF metamagnets (MM) and has been studied for more than three decades In this MM in addition to the rapid rise in the magnetization at a critical field Bc = 20 T applied in the basal plane (θ = 00) the longitudinal ultrasound velocity[9] suffers an enormous reduction. In this report we present new high field and very low temperature high resolution measurements of the sound velocity, magnetostriction and magnetization in UPt3 which reveal a complex and rich anisotropic behavior. We present US measurements for fields oriented away from the c-axis from which we obtain the angular dependence of the newly observed transitions
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