Study On The Magnetic Properties Of RE₆Fe₁₃M Compounds With “Table-like” Magnetocaloric Effect

Magnetic refrigeration technology with the advantages of high efficiency,energy conservation,environmentally is considered as the most promising refrigeration technology to replace traditional refrigeration technology.In recent years,magnetocaloric materials as the core of magnetic refrigeration technology have attracted a lot of attention.Based on the various magnetic properties of Nd₆Fe₁₃Pd compound,in this paper,RE₆Fe₁₃M?RE=Nd,Gd,Tb,Dy,Ho,Er;M=Pd,Ge,Ag,In,Sn,etc.?and Nd₆Fe₁₃Pd X?X=H,C?series alloys were obtained through the means of elemental doping and the introduction of interstitial atoms.The structure,magnetic and magnetocaloric properties of the series of alloys were systematically investigated by X-ray Diffraction?XRD?,Scanning Electron Microscope?SEM?,X-ray Energy Dispersive Spectrometers?EDS?and Physical Property Measurement System?PPMS?.The main research results are as follows.The structure,magnetic and magnetocaloric properties of the alloys which the Pd elements in Nd₆Fe₁₃Pd were substituted by Ge,Ag,In,Sn were investigated.The XRD results show that all the doped compounds are monophase.Moreover,the magnetic transition temperature T_tr of these compounds can be adjusted in the temperature range of 76 K?174K with different substitution elements and different substitution quantities.The compounds undergo a first-order magnetic phase transition from the ferromagnetism to anti-ferromagnetism around the T_tr.At the AFM region,there exists a field-induced metamagnetic transition from AFM to FM.Under the magnetic field change of 5 T,the maximum magnetic entropy changes of Nd₆Fe₁₃Pd_1-xGe_x?x=0.1,0.2?alloys are estimated to be 3.73 J kg^-1 K^-1and 1.92 J kg^-1 K^-1,the corresponding RC values are 271.7 J kg^-1and 184.5 J kg^-1,respectively;For the Nd₆Fe₁₃Pd_1-xAg_x?x=0.1,0.2,0.3?compounds,the maximum magnetic entropy changes are estimated to be 4.9 J kg^-1 K^-1,4.5 J kg^-1 K^-1 and 3.5 J kg^-1 K^-1,the corresponding RC values are 327 J kg^-1,315 J kg^-1 and 310 J kg^-1,respectively;For the Nd₆Fe₁₃Pd_1-xIn_x?x=0.1,0.2?compounds,the maximum magnetic entropy changes are estimated to be 3.5 J kg^-1 K^-1 and 3.1 J kg^-1 K^-1,the corresponding RC values are 234 J kg^-1and 223 J kg^-1,respectively;For the Nd₆Fe₁₃Pd_0.8Sn_0.2 compound,the maximum magnetic entropy change and corresponding RC value are determined to be 4 J kg^-1 K^-1 and 264 J kg^-1,respectively.Except the compounds doped with In,other compounds obtained a“table-like”magnetic entropy curve under different field change.The series of compounds are important candidate materials in the field of magnetic refrigeration.The alloys which the Nd elements in Nd₆Fe₁₃Pd were substituted by Gd,Tb,Dy,Ho,Er were prepared.The relative solubility of Gd,Tb,Dy,Ho,Er in 25Nd-5RE-65Fe-5Pd at.%and 27.5Nd-2.5RE-65Fe-5Pd at.%alloys were measured.Single phase Nd_5.7Gd_0.3Fe₁₃Pd and Nd_5.7Tb_0.3Fe₁₃Pd were obtained and the magnetic and magnetocaloric properties of Nd_5.7Gd_0.3Fe₁₃Pd were investigated.The relative solubility of Gd,Tb,Dy,Ho,Er in 25Nd-5RE-65Fe-5Pd at.%and 27.5Nd-2.5RE-65Fe-5Pd at.%alloys were estimated to be 5 at.%and 3 at.%,3.7 at.%and 2.3 at.%,3 at.%and 2.1 at.%,3 at.%and 1.6 at.%,2.7 at.%and 1.4at.%,respectively.The Nd_5.7Gd_0.3Fe₁₃Pd compound undergoes a magnetic phase transition from the ferromagnetism to anti-ferromagnetism around the 210 K.In AFM region,there exists a field-induced AFM-FM first-order magnetic transition.Under the magnetic field change of 5 T,the maximum magnetic entropy change and corresponding RC value for the Nd_5.7Gd_0.3Fe₁₃Pd compound are determined to be 4.4 J kg^-1 K^-1 and 288 J kg^-1,respectively.The compound also obtained a“table-like”magnetocaloric effect and the working temperature extends to the vicinity of room temperature.The interstitial atom H and C were introduced into Nd₆Fe₁₃Pd,and the Nd₆Fe₁₃Pd C_0.5and Nd₆Fe₁₃Pd H₁₅ compounds were obtained.The structure,magnetic and magnetocaloric properties of the two compounds were studied.From the XRD results,it can be seen that both compounds are monophasic,but the difference is that the compounds have tropism behavior in the hydride.Both compounds undergo a magnetic phase transition from FM to AMF,and Nd₆Fe₁₃Pd H₁₅ accompany a wide temperature range.Nd₆Fe₁₃Pd C_0.5 is a first-order magnetic phase transition,but Nd₆Fe₁₃Pd H₁₅ is a second-order magnetic phase transition.Under the magnetic field change of 5 T,the maximum magnetic entropy changes of the Nd₆Fe₁₃Pd C_0.5 and Nd₆Fe₁₃Pd H₁₅ compounds are estimated to be 4.5 J kg^-1 K^-1and2.5 J kg^-1 K^-1,the corresponding RC values are 300 J kg^-1and 235 J kg^-1,respectively.In addition,in the Nd₆Fe₁₃Pd H₁₅ compound,we obtained a“table-like”magnetic entropy curve,and the working temperature of the compound reached 285 K,which was close to room temperature.