MgB_(2)的高压效应研究

Effect of In-situ Hydrostatic Pressure on MgB_(2)

我们研究了高压对MgB_(2)块材超导的超导转变温度T_(c)、临界电流密度J_(c)、不可逆场H_(irr)以及钉扎机制的影响。结果显示压力降低了样品的T_(c)和J_(c),使不可逆线向低场移动。更有趣的是压力使样品中主要的钉扎机制由δT_(c)转变为δl钉扎,即由于缺陷密度的分布导致电子运动的平均自由程在空间的涨落钉扎。另外,通过磁弛豫的测量,结果显示压力加快了磁通的蠕动,降低了有效钉扎能和J_(c),磁通束尺寸的大小变化不大。

We performed a systematic study of the superconducting transition temperature(T_(c)),critical current density(J_(c)),irreversibility field(H_(irr))and flux pinning mechanism in MgB_(2).The T_(c)and J_(c)are significantly decreased for low and high temperature and field,and the H_(irr)line is shifted to lower fields by the HP up to 1.2 GPa.Remarkably,we found that the hydrostatic pressure can induce a transition from theδT_(c)to theδl pinning mechanism.The charge-carrier mean free path fluctuation,δl pinning,is responsible for the pinning mechanism in MgB_(2)at 1.2 GPa.According to the magnetic relaxation measurements,our results show that the pressure reduce the pinning energy and the critical current density,and increase the vortex creep rate.The size of flux bundles is almost constant.