The magnetic phase diagram and transport properties of

Abstract

We have used resistivity measurements to study the magnetic phase diagram of the itinerant antiferromagnet FeGe 2 in the temperature range from 0.3-300 K in magnetic fields up to 16 T. In contrast to theoretical predictions, the incommensurate spin density wave phase is found to be stable at least up to 16 T, with an estimated critical field µ 0 H c of ∼ 30 T. We have also studied the low temperature magnetoresistance in the [100], [110], and [001] directions. The transverse magnetoresistance is well described by a power law for magnetic fields above 1 T with no saturation observed at high fields.We discuss our results in terms of the magnetic structure and the calculated electronic bandstructure of FeGe 2 . We have also observed, for the first time in this compound, Shubnikov-de Haas oscillations in the transverse magnetoresistance with a frequency of 190 ± 10 T for a magnetic field along [001].

Dimensionality Effects in FeGe2 Nanowires: Enhanced Anisotropic Magnetization and Anomalous Electrical Transport

“…1(b) , majority of the wires are aligned on the tape plane, the in-plane magnetization (magnetic field applied parallel to the tape) reflects the azimuthal average contribution of the long axis of all the wires on the tape plane, while the out-of-plane magnetization (field perpendicular to the tape) is the sum of the magnetization of the short axis of all wires. For bulk FeGe 2 , at zero or low field, the propagation vector of the SDW is parallel to [100], the spins lie in the basal plane and are ferromagnetically aligned along the [001] direction ( c axis) 18 , 23 , 24 . Assuming the same magnetic structure persist in the nanowires form, along the wire long axis ([110] direction), antiferromagnetic incommensurate or commensurate SDW states form.…”

“…These structural properties are tightly bound to magnetic properties; the short interatomic Fe-Fe spacing along the c -axis can be expected to order ferromagnetically along the c -axis and antiferromagnetically in the basal plane where the interatomic Fe-Fe spacing is greater. The complexity of this structure-property relationship is seen in neutron diffraction results, where FeGe 2 undergoes two phase transitions when cooling in a magnetic field 18 , 23 , 24 . At 289 K, the material transitions from a paramagnet to an incommensurate SDW state.…”

Оптические свойства монокристалла FeGe-=SUB=-2-=/SUB=-

“…всего на 13%, тогда как сопротивление вдоль тетрагональной оси примерно в два раза больше, чем в базисной плоскости [10]. Чтобы понять причину близости плазменных частот при значи-тельной разнице величин сопротивления, измеренного вдоль оси [001] и в базисной плоскости, учтем, что в тетрагональном кристалле зависимость энергии носите-ля заряда от волнового вектора должна иметь вид 2 оправдывает сделанные нами предполо-жения.…”

“…Эти переходы хорошо проявляются на температурных зависимостях намагниченности и внутреннего трения, однако осо-бенности на температурных зависимостях сопротивле-ния ρ(T ) являются весьма слабыми [6][7][8][9][10].…”

Itinerant antiferromagnetism in FeGe2

“…We have used similar measurements, together with constant temperature, field scans which clearly show the lower phase transition, with a magnetic field applied in the basal plane to determine the magnetic phase diagram for FeGe 2 , shown in Figure 3, the behaviour is similar for a field applied along [100]. [15] In order to fully characterise the ground state of FeGe 2 we have measured the spin dynamics at low temperatures (11 K) using the direct geometry timeof-flight spectrometer HET at ISIS. This instrument allows access to much higher incident neutron energies than the thermal triple-axis measurements of Holden et.…”