  We present spin transport studies on a low-field, room-temperature
magnetoelectric multiferroic polycrystalline
$\text{Sr}_{3}\text{Co}_{2}\text{Fe}_{24}\text{O}_{41}$ (SCFO)|Pt
heterostructure wherein a highly tunable transverse conical magnetic phase is
responsible for static and dynamic magnetoelectric coupling. We measured
angular dependence of spin Hall magnetoresistance (SMR) at constant magnetic
fields ($H$) in the range of 50 to 100 kOe. Application of field below the
critical value (2.5 kOe), yielded negative SMR and the $H$-evolution of
normalized SMR exhibited a negative gradient. Further, an increase in the $H$
resulted in the positive slope of normalized SMR Vs. $H$ and later at higher
$H$ around 14 kOe, a crossover from negative to positive SMR was observed. We
employed a simple model for estimating the equilibrium magnetic configuration
and computed the SMR modulation at various values of $H$. We argue that the
tilting of the cone is dominant and in turn responsible for the observed nature
of SMR below 2.5 kOe while, the closing of the cone-angle is pronounced at
higher fields causing a reversal in sign of the SMR from negative to positive.
Importantly, SMR experiments revealed that a change in the helicity with a
reversal of the magnetic field has no influence on the observed SMR.
Longitudinal spin Seebeck effect (LSSE) signal was measured to be 500 nV at 280
K, under application of thermal gradient, $\Delta T = 23$ K and field, 60 kOe.
The observed LSSE signal, originating from pure magnon spin current, showed a
similar $H$-dependent behavior as that of the magnetization of SCFO. Our
detailed spin transport studies on polycrystalline SCFO|Pt heterostructure
demonstrate high tunability of the amplitude and the sign of the SMR,
highlighting its potential for novel spintronic devices such as SMR-based spin
valves and voltage-controlled spin transport devices.
