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中国科学院物理研究所  通用 实验技术公共课程. 第六讲:仪器的原理与使用 . 《 磁性测量 》. 赵同云 磁学国家重点实验室. 2014年9月26日. 声 明. 本讲稿中引用的图、表、数据全部取自公开发表的书籍、文献、论文,而且仅为教学使用, 任何人不得将其用于商业目的 。. 磁性测量  仪器篇 之一 MPMS 的介绍. 物理所磁学室公共测试讲座. 主 要 内 容. 提拉样品磁强计的原理和型式 步进提拉方式( MPMS ) 匀速提拉方式( ESM 、 ACMS ) 往复提拉方式( RSO )

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中国科学院物理研究所  通用实验技术公共课程

第六讲:仪器的原理与使用 

《磁性测量》

赵同云

磁学国家重点实验室

2014年9月26日


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声 明

本讲稿中引用的图、表、数据全部取自公开发表的书籍、文献、论文,而且仅为教学使用,任何人不得将其用于商业目的。


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磁性测量  仪器篇之一MPMS的介绍


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物理所磁学室公共测试讲座

主 要 内 容

  • 提拉样品磁强计的原理和型式

    步进提拉方式(MPMS)

    匀速提拉方式(ESM、ACMS)

    往复提拉方式(RSO)

  • MPMS的主要功能及其使用

    温度、磁场的控制

    磁矩的检测、功能

    样品、维护、注意事项

共135页


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提拉样品磁强计

Extracting Sample Magnetometer

(ESM)

感谢?


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ESM的基本要求

  • 样品永远在线圈内部

  • 样品平行于线圈轴向运动

  • 类似于平行于轴向的VSM

  • 无法在有极头的磁体系统中使用


Esm 1

ESM1

ESM的基础-1

抛移线圈:冲击法(课程六)

CS, N:线圈磁通常数

迴线仪


Esm 2

ESM2

z

O

y

x

ESM的基础-2

点磁偶极子(point dipole)假设?

检测线圈内的磁场强度:

检测线圈

rc

(x, y, 0)

检测线圈内的磁通量:

(x0, y0, z)

5


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ESM3

与VSM相同的处理方法

样品位于检测线圈的轴线上

平行于轴向的VSM

单匝检测线圈内的磁通量:

单匝检测线圈内的感应电势:


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ESM4

与VSM相同的处理方法

样品偏离轴线  距离

平行于轴向的VSM

单匝检测线圈内的磁通量: n=2

单匝检测线圈内的感应电势:n=2


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ESM5

+

一级梯度线圈

与VSM相同的处理方法

一级梯度线圈(串联反接的两个相同线圈)

平行于轴向的VSM


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ESM6

+

二级梯度线圈 (MPMS)

与VSM相同的处理方法

二级梯度线圈(串联的两组一级梯度线圈)

平行于轴向的VSM


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磁通量与点磁偶极子位置

单匝检测线圈:可以测量均匀磁场的变化

ESM

?


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磁通量与点磁偶极子位置

一级梯度线圈:可以抵消均匀磁场

ACMS

VSM

10


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磁通量与点磁偶极子位置

二级梯度线圈:可以抵消均匀的背景

MPMS

SVSM


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ESM6

ESM仪器设备

ESM的原理:积分式磁强计

ε

  • 提拉速率:高

  • 使用积分器

  • 磁矩定标:Ni

  • 灵敏度低于VSM

  • 开路测量

+

t

0

t0

2t0


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ESM7

ESM仪器设备

ESM的构成

其中,

  • 均匀磁场:

  • 样品提拉系统:

  • 信号采集系统:

  • 测量控制系统

清零


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ESM8

ESM仪器设备

ESM:磁矩的检测


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ESM9

提 拉 样 品 磁 强 计

ESM的现状

  • 单点测量时间短、灵敏度略低;

  • PPMS_ACMS的直流磁性测量采用提拉法;

  • MPMS、MPMS XL的直流磁性测量;

  • 磁学室原有一台ESM(CF-1型);

  • 现在已经很少有独立的ESM。

15


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几种ESM的介绍

  • 步进提拉方式(MPMS)

  • 匀速提拉方式(ESM、ACMS)

  • 往复提拉方式(MPMS_RSO)


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+

+

+

+

二级梯度线圈 (MPMS)

二级梯度线圈 (MPMS)

二级梯度线圈 (MPMS)

一级梯度线圈(ESM)

步进、匀速、往复


Mpms mpms xl

MPMS、MPMS XL

  • 基本工作原理

  • 各种功能的介绍

  • 使用中的注意事项

  • 人身、财产安全

  • 样品几何、安装

  • 具体功能的限制


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MPMS1

MPMS的原理

QD_MPMS(XL)

By MikeMcElfresh

Fundamentals of Magnetism and Magnetic Measurements

Featuring Quantum Design’s Magnetic Property Measurement System

http://www.qdusa.com/sitedocs/appNotes/mpms/FundPrimer.pdf


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名词:超导量子磁强计

中华人民共和国计量技术规范 JJG 1013-89

《磁学计量常用名词术语及定义(试行)》

4.95 超导量子磁强计:

Superconducting Quantum magnetometer

中文:超导量子磁强计;SQUID磁强计

英文:SQUID Magnetometer;

SQUID (Superconducting Quantum

Interference Device) Magnetometer

20


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量子设计公司及其产品


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DOU升级了

超导室(MPMS-5S)、磁学室(MPMS-7)

15

10

2

5


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课后作业-1

你知道MPMS具体细节的哪些内容?

对于MPMS XL新功能有何评价?


The chronology

After Bill of QD, 2006

The Chronology

  • 1911 – Heike Kammerlingh Onnes discovers superconductivity

    • 1913 Receives the Nobel Prize in Physics

  • 1962 – Brian Josephson predicts the “Josephson Effect”

    • 1973 Receives the Nobel Prize in Physics

  • 1986 – Bednorz and Muller discover High Temperature Superconductivity

    • 1987 They receive the Nobel Prize in Physics


The squid

After Bill of QD, 2006

The SQUID

  • Within a year of Brian Josephson’s discovery, the first Superconducting Quantum Interference Device (SQUID) was built

  • In 1968, Professor John Wheatley of UCSD and four other international physicists founded S. H. E. Corp. (Superconducting Helium Electronics) to commercialize this new technology.

25


Squid magnetometers

After Bill of QD, 2006

SQUID Magnetometers

  • The first SQUID magnetometer was developed by Mike Simmonds, Ph.D. and Ron Sager, Ph.D. while at S.H.E. Corporation in 1976.

  • In 1982, Mike and Ron, along with two other SHE employees, founded Quantum Design.

  • In 1984, QD began to market the next generation SQUID magnetometer – the Magnetic Property Measurement System (MPMS).

  • In 1996, QD introduced the MPMS XL as the latest generation SQUID magnetometer

  • During the past 22 years, six companies have unsuccessfully designed and marketed SQUID magnetometers to compete with the MPMS.

26


Mpms xl temperature control

After Bill of QD, 2006

MPMS XL Temperature Control

  • Patented dual impedance design allows continuous operation below 4.2 K

  • Sample tube thermometry improves temperature accuracy and control

  • Transition through 4.2 K requires no He reservoir refilling and recycling (no pot fills)

  • Temperature sweep mode allows measurements while sweeping temperature at user controlled rate

    • Increases measurement speed

  • Smooth temperature transitions through 4.2 K both cooling and warming


Mpms xl temperature control1

After Bill of QD, 2006

MPMS XL Temperature Control

MPMS、SQUID_VSM:独立的温度、气氛环境


Mpms xl temperature control2

After Bill of QD, 2006

MPMS XL Temperature Control


Mpms xl temperature control3

我的评价

MPMS XL Temperature Control

30


Mpms xl temperature control4

我的评价

MPMS XL Temperature Control

Set Temperature 10 K

Wait for temperature stable 30 min

70 min


Mpms xl temperature control5

我的评价

MPMS XL Temperature Control

OverShoot!

Stabilizing!

JIm (QD):

The idea is just to wait some extra time for upper section (stainless steel slow to change) of sample tube to cool down and get lower thermal gradient. Otherwise, the extra heat load will prevent stabilizing and/or holding 2 K.


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在10 K快速稳定的小技巧

程序设定:

  • 重复设定温度10 K

Set Temperature 10.000K at 10.000K/min.

Waitfor Delay:1800secs

Set Temperature 10.000K at 10.000K/min.

Waitfor Delay:300secs

Set Temperature 10.000K at 10.000K/min.

Waitfor Delay:300secs

Set Temperature 10.000K at 10.000K/min.

Waitfor Delay:300secs

手动:

Set Temperature 10 K


Wait for

Wait for

  • Wait for

  • Wait for Temp Stable

  • Wait for Temperature

  • Wait for Field

  • Wait for Position


Mpms xl temperature control6

After Bill of QD, 2006

MPMS XL Temperature Control

  • Temperature Range: 1.9 - 400 K (800 K with optional oven)

  • Operation Below 4.2 K: Continuous

  • Temperature Stability: ±0.5%

  • Sweep Rate Range: 0.01 - 10 K/min with smooth transitions through 4.2 K

  • Temperature Calibration ±0.5% typical Accuracy:

  • Number of Thermometers: 2 (one at bottom of sample tube; one at the location of sample measurements)

35


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MPMS2

两种控温模式


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MPMS3

温度

+

T1

-

20 秒

40 秒

时间

显示

QUENSQ

控温模式:单点设定温度

设定温度 :T 1Kelvin

Set Temperature to :T 1Kelvin

升 温

测 量

Tolerence

显示温度

实际温度

如果温度在T1内

系统认为温度稳定

=0.005  T 1


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MPMS4

温度

T1

2

时间

控温模式:单点设定温度

降 温 测 量 ?

实际温度

显示温度


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MPMS5

扫描到 某一温度

设定 起始温度

设定 变温速率

扫描到 某一温度

控温模式:扫描温度

扫描温度到 :T SKelvin

Set Temperature to:T 1 Kelvin

Sweep Rate:1 mK/min~10 K/min

Sweep Temperature to :T SKelvin


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MPMS6

测量

结束/开始

温度

测量过程中

温度变化

测量

开始/结束

T F

T S

时间

控温模式:扫描温度

同时进行升 温、降 温 测 量

T = (T S+T F)/2

Sweep Temperature

40


Magnetic field control

Very high homogeneity magnets (1, 5 and 7 Tesla)

0.01% uniformity over 4 cm

Magnets can be operated in persistent or driven mode

Hysteresis mode allows faster hysteresis loop measurements

Magnets have two operating resolutions: standard and high resolution

After Bill of QD, 2006

Magnetic Field Control


Hysteresis measurement

After Bill of QD, 2006

Hysteresis Measurement


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MPMS7

SQUID磁强计 磁场控制示意图

I

电源开关

K

I2

I1

超 导 开 关

开 关 电 阻 r

闭环:r = 0;I2 = -I1

开环:r = rn;I2 = 0

电源

闭环运行

开环运行

E

不加热

加热

R

可调电阻

液 氦

超导磁体


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MPMS8

电源电流

开关状态

线圈电流

开关电流

磁场 升

磁场 降

SQUID磁强计 磁场升-降过程


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MPMS9-1

磁场变化的模式

开环模式:Hysteresis Mode

开关电阻为正常态;

电源与超导磁体线圈保持接通;

实际磁场与设定值相差一小量。

闭环模式:No Overshoot Mode

闭环模式:Oscillate Mode

H

45


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MPMS9-2

开环运行时的磁场噪声

开环模式:Hysteresis Mode


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关于变场速率

  • 电感-电源电压

Lcoil:20 H ~ 35 H

source:2.0 V ~ 5.0 V


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MPMS10

关于变场速率

  • 电感-电源电压

117 Oe/s ~ 515 Oe/s

2062.71 Oe/A

磁场/电流比:(线圈几何灵敏因子)


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VSM7

互易性原理

课程三

均匀磁化(homogeneous magnetization)

gcoil:几何(位置)灵敏因子

I

rc

z(t)

m

 圆形电流线圈的磁场(春)

小样品!


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MPMS11

MPMS-7型超导量子磁强计介绍

纵向探测系统:Longitudinal Moment Detection System

QUENSQ

50


Squid

MPMS12

SQUID磁强计磁矩检测系统

为什么要调节样品的中心位置

样品架

Straw-like


Reciprocating sample measurement system rso

After Bill of QD, 2006

Reciprocating Sample Measurement System(RSO)


Reciprocating sample measurement system rso1

After Bill of QD, 2006

Reciprocating Sample Measurement System(RSO)

  • Frequency Range:0.5 - 4 Hz

  • Oscillation Amplitude:0.5 - 50 mm

  • Relative Sensitivity:<1 x 10-8 emu; H  2,500 Oe, T = 100 K (for 7-tesla magnet)

     6 x 10-7 emu; H @ 7 tesla, T = 100 K (for 7-tesla magnet)

  • Dynamic range10-8 to 5 emu (300 emu with Extended Dynamic Range option)


Mpms rso

MPMS RSO 1

MPMS RSO的原理

单匝检测线圈内的磁通量:

原理上的可行性

单匝检测线圈内的感应电势:


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磁通量与点磁偶极子位置

二级梯度线圈:可以抵消均匀的背景

RSO

MPMS

SVSM

55


Mpms rso1

MPMS RSO 2

+

二级梯度线圈

MPMS RSO的原理

二级梯度线圈内的磁通量:

原理上的可行性


Mpms rso2

MPMS RSO 3

MPMS RSO的原理

二级梯度线圈内的磁通量对位置的导数:

原理上的可行性

rc=0.97 cm

=1.519 cm

只与线圈的尺寸和相对位置有关,是确定的。

MPMS XL:0.62 cm(QD)、0.587 cm(计算)


Mpms rso3

MPMS RSO 4

MPMS RSO的使用

1、硬件:使用伺服马达驱动

专用RSO传输台(RSO motor)

2、功能:实现MPMS的快速测量

磁矩~磁场、温度关系

3、适用性:磁矩上限:0.5 emu?

仅适用于所有的磁性测量

JIm:

Yes, EDR is automatically enabled with RSO, whenever over-range error reported at normal maximum 1.25 emu scale.


Mpms rso4

MPMS RSO 5

MPMS RSO的使用

硬件:专用RSO传输台(RSO motor)


Mpms rso5

MPMS RSO 6

MPMS RSO的使用

可以在任何温度取放样品!

必须100 K以上温度取放样品!

样品取放:Air Lock

60


Mpms rso6

MPMS RSO 7

MPMS RSO的使用

原则上,中心位置仍然是最佳选择-Jim

4、样品位置:中心、最大斜率?

弱磁性信号的样品

对磁场均匀性敏感的材料

必须对称!必须地!


Mpms system options

Transverse Moment Detection

for examining anisotropic effects

Second SQUID detection system

SQUID AC Susceptibility

2 x 10-8 emu sensitivity 0.1 Hz to 1 kHz

Ultra-Low Field

Reduce remanent magnet field to ±0.05 Oe

Extended Dynamic Range

Measure moments to ±300 emu

External Device Control

Control user instruments with the MPMS

10 kBar Pressure Cell

Sample Rotators

Vertical and Horizontal

Sample Space Oven

Temperatures to 800 K

Environmental Magnetic Shields

Fiber Optic Sample Holder

Allows sample excitation with light

Manual Insertion Utility Probe

Perform elector-transport measurements in MPMS

Liquid Nitrogen Shielded Dewar

EverCool Cryocooled Dewar

No-Loss liquid helium dewar

No helium transfers

After Bill of QD, 2006

MPMS System Options

13+1


Transverse moment detection

After Bill of QD, 2006

Transverse Moment Detection

  • Measures anisotropic effects of moments with vector components perpendicular to the applied field

  • Incorporates a second SQUID detection system which can resolve transverse moments as small as 10-6 emu

  • Second-order detection coils orthogonal to the longitudinal detection coils


Squid ac susceptibility

After Bill of QD, 2006

SQUID AC Susceptibility

  • Dynamic measurement of sample

    • Looks also at the resistance and conductance

    • Can be more sensitive the DC measurement

  • Measures Real () and Imaginary () components

    •  is the resistance of the sample

    •  is the conductive part

      • Proportional to the energy dissipation in the sample

  • Must resolve components of sample moment that is out of phase with the applied AC field

    • SQUID is the best for this because it offers a signal response that is virtually flat from 0.01 Hz to 1 kHz

  • Available on all MPMS XL systems

  • Requires system to be returned to factory for upgrade


Squid ac susceptibility1

After Bill of QD, 2006

SQUID AC Susceptibility

  • Features

    • Programmable Waveform Synthesizer and high-speed Analog-to-Digital converter

    • AC susceptibility measured automatically and can be done in combination with the DC measurement

    • Determination of both real and imaginary components of the sample’s susceptibility

    • Frequency independent sensitivity

  • Specifications

    • Sensitivity (0.1 Hz to 1 kHz):2 x 10-8 emu @ 0 Tesla

      1 x 10-7 emu @ 7 Tesla

    • AC Frequency Range:0.01 Hz to 1 kHz

    • AC Field Range:0.0001 to 3 Oe (system dependent)

    • DC Applied Field:±0.1 to 70 kOe (system dependent)

65


Squid ac susceptibility2

After Bill of QD, 2006

SQUID AC Susceptibility


Ultra low field capability

After Bill of QD, 2006

Ultra-Low Field Capability

  • Actively cancels remanent field in all MPMS superconducting magnets

  • Sample space fields as low as ±0.1 Oe achievable

  • Custom-designed fluxgate magnetometer supplied

  • Includes Magnet Reset

  • Requires the Environmental Magnet Shield


Hysteresis measurement1

After Bill of QD, 2006

Hysteresis measurement


Extended dynamic range

After Bill of QD, 2006

Extended Dynamic Range

  • Extends the maximum measurable moment from ± 5 emu to ± 300 emu (10 orders of magnitude)

  • Automatically selected when needed in measurement

  • Effective on both longitudinal and transverse SQUID systems


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关于MPMS的量程

  • 基本量程(Primary Dynamic Range)

  • 扩展量程(Extended Dynamic Range)

70


Mpms 1

关于MPMS的量程(1)

DC Transport:

4 cm, 32-point scan

  • 基本量程(Primary Dynamic Range)

1.25 emu

4 cm, 64-point scan

Holding: 64 points per scan

RSO:

0.4 emu

10.0 emu

> 10.0 emu ?


Mpms 2

关于MPMS的量程(2)

DC Transport:

每步: 10 V

  • 点数(提拉步数)与量程

RSO:

每步: 5 V


Mpms 3

关于MPMS的量程(3)

300 emu

DC Transport:

RSO:

  • 扩展量程(Extended Dynamic Range)

4 cm, 64-point scan

JIm:

EDR basically just puts atransformer between pick-up coil and SQUID capsule to reduce currentgenerated in gradiometer by very large signals.

While we of course calibrate the impact from extra electronic components, there will always be a distinct step in the data at this transition.


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SQUID13

B=0

SQUID

检测电路

Mf

Output

rf

if

超导量子干涉器件的应用

课程二

M

x

磁通的间接测量:电流负反馈

i,LLead

L

Ls,Ns

Lp,Np

间接使用


Sample space oven

After Bill of QD, 2006

After Bill of QD

Sample Space Oven

  • Provides high temperature measurement capability

    • Ambient to 800 K

  • Easily installed and removed by the user when needed

  • A minimal increase in helium usage

    • Approximately 0.1 liters liquid helium/hour

  • 3.5 mm diameter sample space

75


Mpms horizontal rotator

After Bill of QD, 2006

MPMS Horizontal Rotator

  • Automatically rotates sample about a horizontal axis during magnetic measurement

  • 360 degrees of rotation; 0.1 degree steps

  • Sample platform is 1.6 X 5.8

  • Diamagnetic background signal of 10-3 emu at 5 tesla

(课程一):样品总磁矩 < 0.1 memu


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QD公司SQUID磁强计的升级

 Sample Rotator for MPMS

?


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水平旋转台

  • 打滑


Manual insertion utility probe

After Bill of QD, 2006

Manual Insertion Utility Probe

  • Perform electro-transport measurement in the MPMS sample space

  • 10-pin connector

  • Use with External Device Control (EDC) for controlling external devices (e.g., voltmeter and current source)

    • Creates fully automated electro-transport measurement system


Http www qd china com upfile news 201071245437533 pdf

http://www.qd-china.com/upfile/news/201071245437533.pdf

80


External device control

After Bill of QD, 2006

External Device Control

  • Allows control and data read back from third party electronics

  • Allows custom control of MPMS electronics

  • Use with Manual Insertion Utility Probe for automated electro-transport measurements

  • MPMS MultiVu version written in Borland’s Delphi (Visual Pascal) programming language


Hysteresis measurement made with external device control edc

After Bill of QD, 2006

Hysteresis Measurementmade with External Device Control (EDC)

  • Using EDC to control a DC field using the AC coil in the MPMS

  • Up to ± 8 Oe DC field (system dependent)

  • Step size as small as 1.9 Oe

20 Å Ni Thin Film (PSI, Zurich)


Fiber optic sample holder

After Bill of QD, 2006

SMA connector

Slide seal

Fiber optic bundle

Fiber Optic Sample Holder

  • Allows sample to be illuminated by an external light source while making magnetic measurements

  • Optimized for near UV spectrum (180 to 700 nm)

  • Includes 2-meter fiber optic bundle

  • Sample bucket 1.6 mm diameter and 1.6 mm deep

Firberguide Industries: Superguide G UV-Vis fiber


Http www qd china com upfile news 201071245437533 pdf1

http://www.qd-china.com/upfile/news/201071245437533.pdf

  • 只与磁性测量兼容


Mpms liquid helium dewar options

After Bill of QD, 2006

MPMS Liquid Helium Dewar Options

  • Basic system supplied with a vapor shielded 56 liter dewar

  • Liquid nitrogen jacketed version of the basic dewar improves hold time by ~ 30%

  • MPMS EverCool Cryocooled Dewar

85


Mpms evercool dewar

After Bill of QD, 2006

MPMS EverCool Dewar

  • Designed to eliminate the need for liquid helium transfers

  • Virtually eliminates all helium loss from the Quantum Design MPMS magnetometer system

  • Cryocooler-dewar system that recondenses the helium directly in the dewar

  • Integrated into MPMS Operating System

  • Cryocooler operation can be controlled automatically to minimize interference with sensitive magnetic measurements

  • Available as an upgrade to all MPMS systems (no equipment needs to be returned to Quantum Design)

  • Available with water or air cooled compressor


Mpms evercool dewar1

After Bill of QD, 2006

MPMS EverCool Dewar

Cryocooler

coldhead

Liquid helium

condenser unit

非常感谢物理所建立了低温条件保障中心!

向在低温车间辛勤劳动的全体人员致敬!


Mpms evercool dewar2

After Bill of QD, 2006

MPMS EverCool Dewar


New product high pressure cell

After Bill of QD, 2006

New Product: High Pressure Cell

  • Manufactured by easyLab Limited in the UK

  • Offers 10 kbar of pressure

  • Supplied with complete user’s kit

M06组


New product 3 helium system

After Bill of QD, 2006

New Product: 3Helium System

  • Minimum temperature of 0.48K

  • Manufactured and marketed by IQUANTUM of Japan

90


4844108

MPMS操作 1

超导量子磁强计的操作

  • 超导量子磁强计的运行(条件)

  • 样品的安装(原则与方法)

  • 控制软件的启动和使用(方法)

  • 测量程序的编辑(过程)

  • 数据文件的处理(注意事项)


4844108

MPMS操作 2

安全

超导量子磁强计的操作

认真阅读仪器的《使用手册》

严格按照操作程序操作

我本人非常同情黄伟文同志…的…


4844108

MPMS操作 3

超导量子磁强计的操作

  • 超导量子磁强计的运行(条件)

    1、使用液氦

    总容量:56 升;初次冷却:100 升;

    液氦的自然蒸发:3 升 ~ 5 升/天(5 K时)

    30 %以下:必须输入液氦;50 %以上:5 T磁场

    2、电力要求

    交流(2205 %)V

    3、环境要求

    温度(< 30 C)、湿度(< 80 %)


4844108

样品安装 1

超导量子磁强计的操作

  • 样品的安装(原则与方法)

  • 探测线圈的设计原理

    超导量子磁强计的磁矩探测线圈采用 Second-order Gradiometer

    几何构形。最主要特点是:当一个均匀的长样品在探测线圈中

    移动时,只要样品的长度远远大于探测线圈的长度,则该样品

    在探测线圈中不会产生信号。

  • 样品架的选择  石英管、吸管

    厚度均匀、质量轻、密度低、磁化率小、热稳定性高

  • 安装样品的方法(推荐)

    样品尺寸缩小、样品径向居中、内外压力平衡、样品刚性安放


4844108

95


4844108

样品安装 2

9 mm

6 mm

H

超导量子磁强计的操作

  • 磁性测量样品的安放原则

1、样品尺寸尽量小

2、样品在磁场方向对称

3、样品在径向居中

4、刚性固定


4844108

关于薄膜样品

  • 样品尺寸、方向

L

L


4844108

+

二级梯度线圈

关于薄膜样品

  • 样品尺寸、方向(竖直放置)


4844108

关于薄膜样品

  • 样品尺寸、方向(竖直放置)


4844108

+

二级梯度线圈

关于薄膜样品

  • 样品尺寸、方向(水平放置)

100


4844108

关于薄膜样品

  • 样品尺寸、方向(水平放置)


4844108

关于薄膜样品

M

  • 样品尺寸、方向(比较:5点)

1.117

1.000

0.936

O

H

5 mm  5 mm


4844108

关于薄膜样品

  • 样品尺寸、方向(比较:均匀磁化)

L

L


4844108

关于弱磁性信号的样品

MPMS XL、VSM

  • 背景、背景的扣除

自动扣除背景:

能用!

信号:~ 1.05

信号:~ 0.10

信号:~ 100

背景:~ 1.00

背景:~ 1.00

背景:~ 10


4844108

关于弱磁性信号的样品

关于胶带:

Kapton

  • 降低背景信号

足够长(> 6 cm)

105


4844108

关于弱磁性信号的样品

  • 粉末

只测量内禀参数:

足够长(> 6 cm)


4844108

样品安装 3

A

B

C

D

超导量子磁强计的操作

  • 样品的安放:磁性测量样品

径向定位

平衡压力用微孔


4844108

脱脂棉

样品

如何判断样品的安装质量(1)

  • 对称性;

  • 多次调节中心的重复性

理想情况的响应曲线

足够长(> 6 cm)


4844108

如何判断样品的安装质量(2)

响应曲线:薄膜样品

L

理想情况的响应曲线

L


4844108

如何判断样品的安装质量(3)

响应曲线:圆柱体样品

H

理想情况的响应曲线

D

110


4844108

样品5

吸管

胶囊

脱脂棉

样品

样品的总磁矩

课程一

样品架(非样品)的磁矩:

对称性!

H

磁矩中心


4844108

样品安装 4

L

L

L

超导量子磁强计的操作

  • 样品的安放:电性(接触)测量样品

  • 两端法:外加电流,测电压(电流与电压共线)

  • 四端法:外加电流,测电压(电流与电压不共线)

  • 两端法:外加电压,测电流(电流与电压共线)

  • van de Pauw 法:

  • 霍耳效应测量:


4844108

物理存在

关于电输运的测量

热电势(温差电势)

  • 根本问题-连线、接触点

异质材料之间的接触电势

热电偶


4844108

同质材料

Meter

同质材料

关于电输运的测量

电阻 < 0 ?

V+

V-

清洁表面、助焊剂、超声压焊

  • 常见问题-虚焊

Iout

Iin

  • 注意事项-消除温差电势

两引线应该使用相同材料;

异质材料的连接点应该处于相同的温度;

同质材料的两端的温度应该相同

环境电噪声


4844108

课后作业-2

在测量电阻时,需要考虑哪些因素?

不同的阻值范围,采用的测量方法有何不同?

115


4844108

MPMS维护 1

100%

液氦

60%

磁场

温度

50%

40%

30%

液面计

超导量子磁强计的维护及注意事项

  • 液氦、温度、磁场


4844108

MPMS维护 2

超导量子磁强计的维护及注意事项

  • 液氦液面与最大可使用的磁场


4844108

MPMS维护 3

He

超导量子磁强计的维护及注意事项

1、控制用计算机

严禁修改MPMSR2快捷方式的设置

软盘必须查/杀病毒

2、样品室

保持样品室清洁(准确度)

保证样品杆密封(下页)


4844108

MPMS维护 4

M

T

超导量子磁强计的维护及注意事项

  • 保持样品腔的清洁(验证、检查)

1、在样品杆上安装一支干净的空吸管;

2、设定磁场1.0 T(闭环);

3、测量M~ T曲线(1.8 K ~ 300 K);

4、验证。

~ 108 emu


4844108

MPMS维护 5

超导量子磁强计的维护及注意事项

  • 保持样品杆密封良好(防止结冻、固态氮氧)

Grease seal

注意O圈

120


4844108

样品室有大量空气凝结的结果

  • 固态O2的反铁磁峰


4844108

样品室密封

5.6 mmole

  • 经历固-液转变点


4844108

样品室连续抽气

5.6 mmole

  • 经历固-液转变点


4844108

举轻若重

400元/升

2000年:~50 元/升;2007年:80元/升;2009年:~200元/升

  • 液氦的价格

  • 氦的密度

1 kg液氦~8 L液氦;1 L液氦 ~ 700 L氦气

氦气 (273 K, 1 atm):0.178 47 g/L;液氦:0.124 98 kg/L

氦气 (273 K, 1 atm):5 603 L/kg;液氦:8.001 3 L/kg

  • 人的肺活量:~ 3.5 L

1 块钱!

~ 15 呼吸/分钟


Mpms xl

MPMS XL的新功能

  • Multiple Measure

125


Mpms xl1

MPMS XL的新功能

  • Multiple Measure (Sequence Command)


Mpms xl2

MPMS XL的新功能

  • Multiple Measure


Mpms xl3

MPMS XL的新功能

  • Multiple Measure命令的使用


Mpms xl4

MPMS XL的新功能

  • Multiple Measure命令的使用


Mpms xl5

MPMS XL的新功能

  • Multiple Measure

n

m

k

130


4844108

剔除异常值的方法

观测值个数 3

  • 国家标准

GB/T 4883-1985

《数据的统计处理和解释 正态样本异常值的判断和处理》

GB/T 8056-1987

《数据的统计处理和解释 指数样本异常值的判断和处理》

检出异常值的个数不超过 1:

MPMS XL:

Multiple Measure

Grubbs检验法、Dixon检验法

检出异常值的个数上限大于 1:

偏度-峰度检验法、Dixon检验法


4844108

实验标准偏差

n次测量结果:x1, x2, …, xi, …, xn

Bessel公式

单次测量的分散性


4844108

实验标准偏差

Bessel公式

n=2:x1, x2

或者都保留

或者都剔除


4844108

为什么

x1=1.456 9、 x2=2.038 7

  • 两个数据点


Mpms xl6

MPMS XL的新功能

  • Multiple Measure

n>2

mn

ks(x)

135


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