Study On The Magnetism Of Magnetic Chiral Soliton Material YbNi₃Al₉

Recently,the chiral topological magnetic configuration has attracted widespread attention in magnetics.This special magnetic configuration is usually found in chiral magnet with DM(Dzyaloshinskii-Moriya)interaction.Due to the lack of inversion symmetry,the spin and orbit in the non-central symmetric structure are coupled,which resulting in DM interaction.The magnitude of DM interaction is weaker than ferromagnetic exchange,and the result of the competition between the two interactions is the chiral helimagnetic order(CHM),which is the chiral magnetic ground state.By using the external field,CHM can be modulated into spin configuration,such as chiral skymion,chiral magnetic bobber,chiral soliton lattice(CSL).These configuration are topological protection,nanometer size and current driven.Therefore,they can be used as potential materials for the next generation of electronic spin devices.At present,it is found that the materials of magnetic solitons are only CrNb3S6 and YbNi3Al9.This article is focus on YbNi3Al9,and the full text of the work are as follows:In the first chapter,we give an brief description of the definition,physical properties and experimental methods of chiral soliton lattice in chiral helimagnetic.First,the theory of the formation of chiral soliton lattice are introduced,including the relationship between the chiral structure and CHM,the microscopic origin of DM interaction and the formation condition and processes of magnetic soliton.Then,the properties of YbNi3Al9 are introduced in detail from five aspects:crystal structure,electricity,specific heat,heavy fermion and magnetism.The second chapter mainly investigate the magnetism and critical phenomenon of YbNi3Al9.As H?c,a magnetic step with loop can be observed in the field-dependent magnetization,which may be corresponding to the possible chiral magnetic soliton phase transition.Based on the analysis of isothermal magnetization around Tc,the critical exponents are obtained as ?=0.1307(2),?=0.17955(4),?=14.1043(7),which fulfill the Windom scaling relation and Rushbrooke's law.The critical exponents are close 2D-Ising mode with spatial-dimensionality n=2 andspin-dimensionality d=1,which reveals that the field-induced magnetic transition for two-dimensional YbNi3Al9 is one-dimensional magnetic coupling.In the third chapter,we have studied the field-induced magnetic transition in different crystal structure oritiation for layered YbNi3A19.We found that two independent universal curves of magnetic entropy change can be fitted out for H?c and H//c.According to the universality principle of scaling,the extra magnetic entropy change(?)caused by the field-induced be obtained.And it is suggested that the (?) for H?c originates from a field-modulated helicoidal spin texture.The (?) for H//c stems from a field-induced canted antiferromagnetic state.In chapter four,the microwave response mechanism of YbNi3Al9 is studied by electron spin response(ESR).When H?c,the ESR spectra show strong response,while it is very weak when H//c.We found that there are two response peaks in the ESR signal of H?c,which are remarked as(?) and(?) increases with the increaing temperature,which is related to the helical magnetic structure of YbNi3Al9.The value of (?) is 20 Oe and nearly unchange,so it may be corresponding to the chiral soliton lattice.Chapter five is the summary and prospect.