Freezing Mechanism of Spins in Reentrant Spin-Glasses

为了阐明重入自旋玻璃的磁性，我们研究了以下合金系统的交流磁化率、磁化强度、磁弛豫、场冷却效应和穆斯堡尔谱。(I)多晶&lt；Fe_(100-x)&gt；&lt；Ni_x&gt；(20&lt；=x&lt；=50)合金；(Ii)单晶&lt；Fe_(65)&gt；&lt；Ni_(35)&gt；(Iii)多晶&lt；(Fe_65Ni_35)_(1-x)(Fe_84Mn_16)_x&gt；(0&lt；=x&lt；=0.26)合金，(Iv)&lt；(Fe_(1-x)M_x)_77&gt；&lt；Si_(10)&gt；&lt；B_(13)&gt；(M=V，Cr，Mn，Co，Ni，0&lt；=x&lt；=1)合金，(V)非晶态&lt；Fe_(100-x)&gt；&lt；(17&lt；=x&lt；=72.5)和&lt；Co_(100-x)&gt；&lt；Sm_x&gt；(50&lt；=x&lt；=70)合金。所获得的结果概括如下：(1)确定了上述各合金系统的磁相图。除&lt；(Fe_(1-x)Co_x)_77Si_10B_13&gt；非晶态合金外，在一定的成分范围内都观察到自旋玻璃相.(2)自旋玻璃与铁磁体之间的转变温度强烈依赖于测量磁场.…(3)对多晶Fe-Ni-Mn和非晶态&lt；(Fe_(1-x)Co_x)_77Si_10B_13&gt；合金的~lt；(57)Fe&g&gt；穆斯堡尔谱分析得到的平均超精细场在&lt；T_g&gt；以下有较大幅度的增加。合金。实验结果表明，非晶态(Fe，Co)-Sm合金中的自旋冻结机制与Fe-Mn合金中的自旋冻结机制不同。(5)非晶态(Fe，Co)-Sm合金中的反铁磁相互作用是由晶体诱导的J混合效应引起的交换增强的RKKY相互作用。(6)其它合金体系中的反铁磁相互作用可能是由于铁原子数量较少而引起的。较低的配位数导致铁自旋受挫。较少

In order to shed light on the magnetism of reentrant spin-glasses, ac susceptibility, magnetization magnetic relaxation, field-cooling effect and Mossbauer spectroscopy on <^(57)Fe> have been investigated for the following alloy systems. (i) Polycrystalline <Fe_(100-x)> <Ni_x> (20<=x<=50) alloys, (ii) Single crystal <Fe_(65)> <Ni_(35)> alloy, (iii) Polycrystalline <(Fe_65Ni_35)_(1-x)(Fe_84Mn_16)_x> (0<=x<=0.26) alloys, (iv) Amorphous <(Fe_(1-x)M_x)_77> <Si_(10)> <B_(13)> (M=V,Cr,Mn,Co,Ni, 0<=x<=1) alloys, (v) Amorphous <Fe_(100-x)> <Sm_x> (17<=x<=72.5) and <Co_(100-x)> <Sm_x> (50<=x<=70) alloys.The obtained results are summarized as follows.(1) The magnetic phase diagram was determined for each alloy system described above. A spin-glass phase was observed in a certain composition range for each alloy system except <(Fe_(1-x)Co_x)_77Si_10B_13> amorphous alloy system.(2) The transition temperature <T_g> between spin-glass and ferromagnet depends strongly on the measuring magnetic field. … More Therefore, the spin-glasses transform into ferromagnet by applying a magnetic field exhibiting a hysteresis loop.(3) The average hyperfine field<H> obtained from analysis of the <^(57)Fe> Mossbauer spectrum exhibits a steeper increase below <T_g> for polycrystalline Fe-Ni-Mn and amorphous <(Fe_(1-x)Co_x)_77Si_10B_13> alloys, while does not for amorphous <Fe_(100-x)> <Sm_x> alloys. These results indicate that the freezing mechanism of spins in the Fe-Sm alloys is different from that in the Fe-Mn alloys.(4) Based on the experimental results the most essential factor leading to spin freezing is the competition between the ferromagnetic and antiferromagnetic interactions in the alloys.(5) The antiferromagnetic interaction in amorphous (Fe,Co)-Sm alloys is a exchange enhanced RKKY interaction caused by the crystal-induced J-mixing effects of <Sm^(3+)> .(6) The antiferromagnetic interaction in other alloy systems may arise from iron atoms which are surrounded by a lower number of iron atom. The lower coordination number causes a frustration of iron spins. Less