The Research Of Glass Forming Ability,Magnetic Property And Magnetic Entropy Behavior Of FeLa(Ce)B Amorphous Alloys

Fe-based amorphous magnetic refrigeration materials have the advantages of low-cost,adjustable Curie temperature（T_c）,and wider refrigeration temperature range,which make it have good development prospect in the field of room temperature magnetic refrigeration.However,the glass forming ability and magneto-caloric effect（MCE）of Fe-based amorphous alloy are poor,which restrict its further development.In order to solve these problems,this paper studies the glass forming ability,magnetic property and magnetocaloric property of Fe La（Ce）B alloys on the basis of the previous research of the research group,aiming to obtain the Fe-based amorphous room temperature magnetic refrigeration material with good glass forming ability and magnetocaloric property.The previous research result shows that Fe₈₅La₃B₁₂amorphous alloy exhibits large-ΔS_m^peak value.However,its T_c（472 K）is relatively high and cannot be used in the field of room temperature magnetic refrigeration.The further research indicates that the T_c of Fe-La-B series amorphous alloys can be changed with the adjustment of the alloy composition and the T_c of Fe₈₈La₃B₉ amorphous alloy is reduced to 432 K.Therefore,the Fe₈₈La_12-xB_x（x=1～11）series alloys are selected for research.The XRD test shows that Fe₈₈La_12-xB_x（x=5～11）alloy ribbons are amorphous structure.The DSC thermal analysis shows that as the B content increases from 5 at.%to 7 at.%,theγparameters andΔT_xincrease,indicating that the glass forming ability of Fe₈₈La_12-xB_x（x=5,6,7）is gradually improved.This may be because the increase in B content makes the grain growth difficult and the amorphous phase more stable.The M-T curves of Fe₈₈La_12-xB_x（x=5～11）amorphous alloys are measured by PPMS,and the Fe₈₈La₇B₅ amorphous alloy with T_c（329 K）close to room temperature is discovered.The isothermal magnetization curve of Fe₈₈La₇B₅ is further measured and combined with the Maxwell relations to calculate its-ΔS_m^peak value is 3.49 JK^-1kg^-1under 5 T,indicating that Fe₈₈La₇B₅amorphous alloy has good magnetocaloric property.The Ce atoms are added to Fe₈₈La₇B₅ amorphous alloy to prepare Fe₈₈La_7-xB₅Ce_x（x=1,2,3,5,7）alloy ribbons.The XRD test shows that Fe₈₈La_7-xB₅Ce_x（x=1,2,3,5,7）alloy ribbons are amorphous structure.According to the characteristic temperature of Fe₈₈La_7-xB₅Ce_x（x=1,2,3,5,7）amorphous alloys measured by DSC thermal analysis,the criteria for glass forming ability such as T_rg andγparameters are calculated,which indicate that the glass forming ability of Fe₈₈La_7-xB₅Ce_x（x=1,2,3,5,7）is higher than Fe₈₈La₇B₅.This may be because the addition of Ce atoms increases the packing density inside the alloy and reduces the driving force for crystallization.Among Fe₈₈La_7-xB₅Ce_x（x=1,2,3,5,7）,the Fe₈₈La₂B₅Ce₅ amorphous alloy has best glass forming ability.The hysteresis loops and M-T curves of Fe₈₈La_7-xB₅Ce_x（x=1,2,3,5,7）amorphous alloy ribbons are measured by PPMS,which indicate that they undergo a ferromagnetic-paramagnetic transition during the heating process and the T_c of them gradually decreases with the increase in Ce content.This may be that the substitution of Ce for La causes the distance between atoms to decrease,which leads to the weakening of the 3d-3d exchange between Fe atoms.According to the isothermal magnetization curves of Fe₈₈La_7-xB₅Ce_x（x=1,2,3,5,7）amorphous alloys measured by PPMS,the-ΔS_m^peak values under different magnetic fields are calculated.It indicates that the-ΔS_m^peak values of Fe₈₈La_7-xB₅Ce_x（x=2,3,5,7）are higher than Fe₈₈La₇B₅ because of the 3d-4f ferromagnetic coupling effect between Fe atoms and Ce atoms,while the-ΔS_m^peak value of Fe₈₈La₆B₅Ce₁is lower than Fe₈₈La₇B₅ because of the influence of nanoclusters.The relationships between-ΔS_m^peak and H of Fe₈₈La_7-xB₅Ce_x（x=1,2,3,5,7）amorphous alloys conform to-ΔS_m^peak∝Hⁿ and the n values obtained by linear fitting method have a certain deviation from the predicted value of the mean field theory,which may be due to the existence of certain middle-range order or even nanocrystalline structure in the amorphous alloys.