Gd substitution induced incommensurate antiferromagnetism in B20 noncentrosymmetric CoSi.

Rare-earth element Gd doped CoSi, Co1-xGdxSi (x= 0.01), is investigated using x-ray diffraction and magnetization. It crystallizes in B20 cubic structure with lattice parameter ofa= 4.4429 Å. The alloy exhibits two antiferromagnetic transitions AFM-I at 38.44 K and AFM-II at 21.87 K followed by an upturn of magnetization belowTut= 9.79 K as illustrated through the temperature-magnetic fieldT-Hphase diagram. AFM-I state is incommensurate. AFM-II state is weakly correlated as inferred from field-induced transition to AFM-I state. Further, AFM-I state is reported to transform to ferromagnetic state in high magnetic fields. The present study stimulates an approach to derive novel and exotic magnetic materials by substituting rare-earth in transition metal monosilicides.

Revealing magnetic and physical properties of TbFe4.4Al7.6: experiment and theory.

We report on the magnetic, electrical transport, caloric and electronic structure properties of TbFe4.4Al7.6polycrystalline alloy using experiment and theory. The alloy crystallizes in tetragonal structure with I4/mmm space group with lattice parametersa = b= 8.7234(5) Å andc= 5.0387(6) Å. It is ferrimagnetic with a compensation temperature ofTcmp∼151 K, Curie-Weiss temperatureθCW∼172.11 K and an effective magnetic momentµeff= (2.37±0.07)µB/f.u withZ= 2. At low temperatures, kinetic arrest-like first-order phase transition is realized through the thermal hysteresis between field-cooled cooling and field-cooled warming curves ofM(T) and virgin curves ofM(H) andρ(H)which are outside the hysteresis loops with metamagnetic transition. The high magnetic field suppression of multiple transitions and reduced coercive fieldHcoerand remnant magnetizationMremwith increasing temperature are reported.HcoerandMremcease to exist above the compensation temperatureTcmp. A correlation between the isothermal magnetization and resistivity is discussed. Specific heatC(T) analysis reveals a Sommerfeld parameter ofγ= 0.098 J⋅mol-1⋅K-2and a Debye temperature ofθD∼351.2 K. The sample is metallic as inferred from theρ(T)behavior and Sommerfeld parameter. The magnetoresistance of the alloy is low and negative which indicates the suppression of weak spin-fluctuations. This alloy avoids the tricritical point despite first-to-second order phase transition. The electronic and magnetic structure calculations, by making use of full potential linearized augmented plane wave method, suggest metallic ferrimagnetic ground state of TbFe4.4Al7.6with Tb atoms contributing ferromagnetically (5.87µB) and Fe atoms with antiferromagnetic contribution (2.67µB), in close agreement with the experimental observation.

Magnetic behavior of Ru substituted skyrmion metal MnSi.

We report on the structural and magnetic properties of Ru substituted skyrmion metal MnSi i.e. Mn1-xRuxSi for the nominal compositions of0⩽x⩽0.5. The composition-temperature (x-T) phase diagram illustrates the substitution-driven changes in the magnetic behavior. It is confirmed that the magnetic ordering temperature (para-to helimagnetic)Ttrand the effective magneticµeffmoment decrease with increasingx. This indicates the suppression of magnetic order by the substitution of Ru in MnSi. However, the magnetic nature is sustained up to a concentration of aboutx= 0.1 above which the system exhibits spin-glass like nature as inferred from the negative Curie-Weiss temperatureθCW, reduced magnetic moment (of the order 10-2 µBf.u.-1) and linearM-H(at 2 K) inx= 0.5. Mn1-xRuxSi is found to avoid the quantum phase transition and exhibits a composition-driven magnetic to spin-glass like transition.